Before they coached, they played. Most of them. On some level. At least in practice.

If there is a common theme among the NFL's 32 head coaches, it's that almost none of them played with the aptitude they now see in front of them on fall Sundays. They might have reached the pinnacle of the coaching profession, but in most cases, it came after recognizing their limits as players.

There is but a single Pro Bowl appearance among them. Two stopped playing after high school, more than a dozen rode the bench in college and only a third advanced to some level of pro football -- be it the NFL, the CFL or the Arena League. Props go to three schools -- Southern California, Idaho State and Pacific -- who each produced two current head coaches.

What follows is a definitive, inarguable and almost entirely subjective ranking of NFL coaches as players. It's based on verified accomplishments of their playing careers, which in some cases meant very little, and features some pretty rad when-they-were-kids photographs. (Looking at you, John Fox.)

A Harbaugh finished atop ESPN.com's ranking of the playing careers for college coaches, but as you'll see, the NFL's Harbaugh doesn't fare quite as well.

Now, on to the rankings:

32. Adam Gase | Miami Dolphins

Courtesy of Marshall Public Schools

Position, top level played: Wide receiver, high school

A Michigan State assistant -- current Baltimore Ravens defensive coordinator Dean Pees -- visited Gase at Marshall (Michigan) High School and gave him his card. When Gase matriculated at MSU, he visited Pees. Rather than discuss walk-on possibilities, the two agreed that Gase would begin an unofficial career as a student-coach.

Something you might not know: As a high school receiver, Gase was "terrible," according to his own oft-repeated assessment. That's objective enough to place him at the bottom of our rankings.

31. Ben McAdoo | New York Giants

Courtesy of Homer-Center High School

Position, top level played: Left tackle, high school

McAdoo thought his best position was defensive line, but regardless, he had no options for playing after high school. He was the first person in his family to attend any college (Indiana University of Pennsylvania). He majored in health/physical education, received a master's degree in kinesiology from Michigan State and -- after having helped out his former high school coach -- decided to go into coaching rather than attend law school.

Something you might not know: McAdoo weighed nearly 230 pounds as a ninth grader but dropped to 180 as a senior at Homer-Center (Pennsylvania) high school. He told the Giants' website: "There wasn't a great market in the college game for a 180-pound left tackle."

30. Chip Kelly | San Francisco 49ers

Courtesy of University of New Hampshire Athletics

Position, top level played: Quarterback and defensive back, FCS

Much has been made of Kelly's incomplete biography, but the accompanying photo confirms Kelly was a part of the early 1980s teams at the University of New Hampshire. He did not play much, or well, during his time there. Mike Murphy, the New Hampshire associate athletic director for communications, said the school has "no discernible stats" for Kelly's playing career. "Let's just say he was a better coach than a player," Murphy said via email.

Something you might not know: That Chip Kelly was on a college football team.

29. Bill Belichick | New England Patriots

Courtesy of Wesleyan Athletics

Position, top level played: Offensive line and tight end, NCAA Division III

Belichick lettered not only in football but also in lacrosse and squash. Wesleyan records do not include playing time, but a school spokesman said Belichick was injured for most of his junior season and saw "limited" action as a senior. He moved almost immediately into coaching after his 1975 graduation, joining the Baltimore Colts as an assistant.

Something you might not know: Football might have been Belichick's third-best sport.

28. Rex Ryan | Buffalo Bills

Courtesy of Southwestern Oklahoma State University

Position, top level played: Defensive line, NCAA Division II

School officials have no documentation that either Rex or his twin brother Rob ever played in a game at Southwestern Oklahoma State University. Rex moved straight into coaching after his 1987 graduation and was named to the school's Hall of Fame in 2012. We used our highly objective and non-biased ranking strategy to place him one spot ahead of Belichick, given the slight difference in competitive level between their schools' conferences.

Something you might not know: The brothers' famous father, Buddy Ryan, had a close friendship with Bob Mazie, SWOSU's head football coach at the time.

27. Mike Zimmer | Minnesota Vikings

Courtesy of Illinois State University Athletics

Position, top level played: Quarterback and linebacker, NCAA Division II

Zimmer matriculated at Illinois State in 1974 in part because his father was close to the coaches there. But two injuries conspired to keep him off the field, and he never played a down of college football. He broke the thumb on his throwing hand during a spring practice before his sophomore season and was moved to linebacker. He then injured his neck, and re-injured it the following year, and eventually had surgery to fuse vertebrae.

Something you might not know: While injured, Zimmer practiced punting in a parking lot so he could do something football-related.

26. John Harbaugh | Baltimore Ravens

Courtesy of Miami University Athletics

Position, top level played: Defensive back, FBS

Harbaugh played sparingly in his career at Miami (Ohio), most notably on special teams as a senior in 1983. At a statue dedication of Harbaugh, he said, "I wasn't a really good football player, but I was the best football player I could ever be." He did win the school's Football Scholar Athlete award.

Something you might not know: There is a statue of Harbaugh at his alma mater, but it depicts him as a coach. (The school is known as a "Cradle of Coaches.")

25. Dirk Koetter | Tampa Bay Buccaneers

Courtesy of Idaho State University

Position, top level played: Quarterback, FCS

Koetter saw some action as a freshman and opened the 1978 season as Idaho State's starter, but a separated shoulder in the season opener ended his season. The resulting surgery derailed his career. He played sparingly as a senior in 1981, completing 31 passes in 54 attempts for 349 yards on a team that won the FCS national championship. An Idaho State biography from the time reported he was the "best student on the team" with a 3.6 grade-point average.

Something you might not know: Koetter was the son of a coach and was a celebrated recruit as a quarterback at Idaho State in 1977.

24. Bill O'Brien | Houston Texans

Courtesy of Brown Athletics

Position, top level played: Linebacker and defensive end, FCS

If you've watched O'Brien's fiery nature on the sideline, or on HBO's "Hard Knocks," you have a decent glimpse of what he was like as a player. He spent his senior season at Brown University as an undersized overachiever who kept after it. "I wasn't terribly athletic," he told the Brown Alumni Magazine. "But I was tough and didn't miss a lot of practices -- your typical grinder." He finished his senior season with 30 tackles and one quarterback sack.

Something you might not know: O'Brien was a trash-talker at Brown. A former teammate told the magazine that O'Brien's voice usually was a whispered rasp by the end of a game.

23. Dan Quinn | Atlanta Falcons

Courtesy of Salisbury University Athletics

Position, top level played: Defensive line, NCAA Division III

Quinn was a productive player for the Salisbury football team but not as decorated as he was in track, in part because of an injury that cost him most of his original sophomore season. After a redshirt season, he appeared in all 28 games during the next three seasons, recording 135 tackles and also returning an interception for a touchdown. He was named to the Salisbury Athletic Hall of Fame in 2005. As the photo shows (No. 99), his shaved-head/goatee look dates back at least 20 years.

Something you might not know: As a two-sport athlete, Quinn set a school record in the hammer throw (168 feet, 0.8 inches). It stood until 2012. That helped him to the 1994 All-Mason-Dixon track and field team.

22. Gus Bradley | Jacksonville Jaguars

Courtesy of North Dakota State University

Position, top level played: Safety and punter, NCAA Division II

A walk-on at North Dakota State who redshirted and then won a scholarship, Bradley intercepted five passes in 40 career games, with most of his time on defense coming in his final two seasons. He punted for four seasons, though, finishing with a career average of 35.5 yards. He helped pave the way for future North Dakota State players to make their way to the NFL. (Quarterback Carson Wentz was the No. 2 overall pick of the 2016 draft.)

Something you might not know: As a player, Bradley was part of three national championship teams for the Bison, including his senior season in 1988.

21. Mike McCarthy | Green Bay Packers

Courtesy of Baker University

Position, top level played: Tight end, NAIA Division II

It's impossible to judge (objectively) the level of competition at Baker (Kansas) University in the mid-1980s, but McCarthy was a standout player there after transferring from Scottsdale (Arizona) Community College. Although the school no longer stores his verified statistics, McCarthy was a two-year starter and earned all-conference honors. In 1986, he was a team captain and Baker finished the season as the NAIA Division II national runners-up.

Something you might not know: McCarthy posed in a ridiculous but hysterical team photo to promote the team (far left).

20. Andy Reid | Kansas City Chiefs

Courtesy of BYU

Position, top level played: Offensive line, FBS

Reid was a 233-pound tackle during his time at Brigham Young from 1978-80. After transferring from junior college, he redshirted in 1978 because of a knee injury and served as a backup in 1979. In 1980, he saw some action on a line that protected BYU quarterback Jim McMahon. Reid joined the school's coaching staff upon graduation in 1981.

Something you might not know: At age 13, Reid appeared live on Monday Night Football in 1971 as part of a punt, pass and kick competition. (A must-see search on Youtube for the video of Reid.)

19. Chuck Pagano | Indianapolis Colts

Courtesy of Wyoming Athletics

Position, top level played: Safety, FBS

Pagano was a two-year starter at Wyoming and played a total of 33 games between 1980-82. Statistics from the time credit him with no interceptions, but he did have nine pass breakups, three fumble recoveries and one forced fumble.

Something you might not know: Pagano played his home games 7,220 feet above sea level at Wyoming; War Memorial Stadium is the highest-standing Division I stadium in the country. That experience might or might not have helped the Colts to one of their biggest victories in Pagano's coaching tenure, a playoff victory in Denver, where Sports Authority Field sits a mere 5,280 feet above sea level.

18. John Fox | Chicago Bears

Courtesy of San Diego State Athletics

Position, top level played: Defensive back, FBS

Fox transferred to San Diego State in 1975 after two seasons at Southwestern College in Chula Vista, California. He broke his collarbone in 1975 and managed only 12 tackles, but in 1976, he played throughout the season and finished with 65 tackles, two pass breakups and an interception.

Something you might not know: That Fox was the first choice to play Jeff Spicoli in "Fast Times at Ridgemont High." (Not really. It's just that his college photo is so ... yeah.)

17. Hue Jackson | Cleveland Browns

Courtesy of Pacific Athletics

Position, top level played: Quarterback, FBS

Jackson shares an alma mater with Pete Carroll and a junior college path with Andy Reid. In two years at Pacific, Jackson was a multi-threat, multi-sport participant after transferring from Glendale Community College. As a senior in 1986, he threw for 1,089 yards and rushed for another 643 yards in 12 games. He also lettered in basketball.

Something you might not know: Jackson went to Pacific preparing for a career as an FBI agent. Instead, he accepted an offer to be a graduate assistant after his time as a player was over.

16. Bruce Arians | Arizona Cardinals

Courtesy of Virginia Tech Athletics

Position, top level played: Quarterback, FBS

Arians landed at Virginia Tech because it was the only program that didn't rescind its interest after he was expelled from high school in the early 1970s. As a college senior in 1974, Arians rushed for 243 yards and what is still a school-record 11 touchdowns. He also threw for 952 yards and another three scores to win the team's MVP award. He moved straight into coaching in 1975.

Something you might not know: Despite his preference for downfield passing as a coach, Arians was a wishbone quarterback at Virginia Tech.

15. Marvin Lewis | Cincinnati Bengals

Courtesy of Idaho State University

Position, top level played: Linebacker and defensive end, FCS

Lewis arrived at Idaho State as a quarterback/safety and saw brief action at both positions before settling into a role as an outside pass-rusher. He recorded 11 sacks in two seasons from 1978-79 and was a second-team All-Big Sky player as a sophomore and junior. He earned honorable mention Big Sky honors as a senior and joined the school's coaching staff after graduation.

Something you might not know: Lewis ran the 40-yard dash in 4.8 seconds as a defensive end in 1978, quite fast for a pass-rusher in those days.

14. Mike Tomlin | Pittsburgh Steelers

Courtesy of William & Mary

Position, top level played: Wide receiver, FCS

Although he became a defense-minded coach, Tomlin started at receiver for three seasons at William & Mary. He was named first-team All-Yankee Conference in 1994 after setting a school record with a 20.4-yard average per catch. In his career, he caught 101 passes for 2,054 yards and 20 touchdowns.

Something you might not know: Tomlin and teammates at William & Mary sometimes acted erratically during pregame warm-ups to unnerve opponents. One told the New York Times that Tomlin would dress to his waist and then do pushups. It was a practice they learned from watching Jim Brown on NFL Films.

13. Pete Carroll | Seattle Seahawks

Courtesy of Pacific Athletics

Position, top level played: Safety, FBS

Carroll transferred to Pacific in 1971 from the College of Marin and was an All-Pacific Coast player for the next two seasons. He finished his senior season with two interceptions and got into coaching after an unsuccessful tryout with the World Football League.

Something you might not know: Probably the most interesting thing that happened to Carroll at Pacific was a near-asphyxiation during his time as an assistant coach there. That's the danger of jumping into a Hail Mary celebration pile, Pete. (Watch Carroll recount the moment in this video.)

12. Jim Caldwell | Detroit Lions

Courtesy of University of Iowa

Position, top level played: Cornerback, FBS

Caldwell's boyhood hero was Gayle Sayers, whom he admired for his quiet disposition off the field and dynamic playmaking on it. Caldwell went on to win a starting job as a freshman; he remained a starter for the rest of his time at Iowa. He was known as a playmaker at a time when the word was just beginning to be used in relation to defensive players, finishing his career with eight interceptions and 21 pass breakups and a total of six blocked kicks.

Something you might not know: Caldwell blocked five kicks as a freshman in 1973, which is still an Iowa school record.

11. Jay Gruden | Washington Redskins

Courtesy of Chris Arnold/Tampa Bay Storm

Position, top level played: Quarterback, World League of American Football (WLAF)

Gruden left the University of Louisville in 1988 as the school's all-time leading passer (7,024) and played one year in the WLAF. After two years of coaching at Louisville, Gruden found his calling in the Arena Football League, where he became one of the best players in league history. A 2012 survey ranked him the second-best quarterback ever to have donned an Arena jersey. Even amid the AFL's pinball statistics, Gruden's are impressive: 21,476 career passing yards, 397 touchdown passes and four coveted ArenaBowl championships. Later, as a head coach, he called himself out of retirement and back on the field for the love of the game.

Something you might not know: There is an Arena Football League Hall of Fame -- and Gruden is in it. He was inducted in 1999.

10. Mike McCoy | San Diego Chargers

Courtesy of Utah Athletics

Position, top level played: Quarterback, NFL (practice squad)

McCoy transferred to Utah, and while you might not remember it, he became one of the nation's top quarterbacks there. He helped the school to consecutive bowl games, finished the 1993 season with the second-most passing yards in the country (3,860) and led the Utes to a 10-2 record in 1994. His pro ambitions took him to the Green Bay Packers' practice squad in 1995, NFL Europe and the Canadian Football League before his retirement in 1999.

Something you might not know: McCoy, 44, once played for George Allen. (Yes, that George Allen.) McCoy was the quarterback at Long Beach State when Allen signed on to coach the 1990 season at age 72. Allen died in December, and a year later, the school disbanded its program.

9. Sean Payton | New Orleans Saints

Courtesy of Chicago Sun-Times

Position, top level played: Quarterback, NFL* (one season)

The height of his career came during the NFL's 1987 strike, when he played in three games for the "Spare Bears" replacement team in Chicago. (*Hence the asterisk above.) Payton completed eight of 23 passes for 79 yards and an interception in those games and also had a 28-yard run. Between his time at Eastern Illinois, where he threw for 10,655 career yards, and the start of his coaching career, Payton also played in the Arena Football League, the Canadian Football League and the UK Budweiser National League.

Something you might not know: Payton played professionally for four leagues in three countries.

8. Doug Pederson | Philadelphia Eagles

Chris Gardner/AP Photo

Position, top level played: Quarterback, NFL (12 seasons)

Yes, Pederson is best remembered as a quarterback for teams that loved his presence in the locker room but had no plans to put him on the field. He backed up Brett Favre in Green Bay, kept the seat warm for Donovan McNabb in Philadelphia and was an emergency backup in Miami when Dan Marino tore his Achilles tendon. Mixed in was one disastrous season with the Browns. According to Pro Football Reference, Pederson's time in Cleveland put him in rare company. He managed just two touchdown passes in eight starts, tied for the second fewest in a season with at least eight starts in the league's post-merger history. Pederson, though, remains one of the best quarterbacks in the history of the University of Louisiana-Monroe.

Something you might not know: Pederson's teams had a .176 winning percentage in his 17 career starts (3-14). The only NFL quarterback with fewer wins in at least 17 starts (since the 1970 merger) is Chris Weinke (two in 20 starts), according to Pro Football Reference.

7. Gary Kubiak | Denver Broncos

Rod Hanna/USA TODAY Sports

Position, top level played: Quarterback, NFL (nine seasons)

Kubiak, an eighth-round draft pick in 1983, made five career starts in place of John Elway. The Broncos went 3-2 in those games, and Kubiak finished his NFL career with 298 attempts. He threw 14 touchdown passes and 16 interceptions. He was perhaps best known for completing 11 of 12 passes in relief of Elway in the 1991 AFC Championship Game. Previously, he had been an All-Southwest Conference quarterback at Texas A&M.

Something you might not know: As Elway's backup in Denver, Kubiak was on the sidelines for 139 of a possible 143 games (97.2 percent) in his career.

6. Jason Garrett | Dallas Cowboys

Pat Sullivan/AP Photo

Position, top level played: Quarterback, NFL (12 seasons)

Garrett impressed everyone he met as a future NFL head coach during his decade-plus as a backup quarterback. But he also was an effective player in his own right. He made nine starts, all for the Cowboys, and won six of them. He threw 11 touchdown passes in 294 career attempts against five interceptions in seven seasons with the Cowboys. He also spent time with the Giants, Buccaneers and Dolphins and made stops in both the CFL and the World League of American Football (WLAF). When he departed Princeton for good after the 1988 season, he ranked second in school history with 4,555 total yards.

Something you might not know: Garrett can claim to have played at not one, but two, Ivy League schools. He began his career at Princeton, transferred to Columbia and then returned to Princeton to become one of the best players in school history.

5. Jeff Fisher | Los Angeles Rams

Herb Weitman/USA TODAY Sports

Position, top level played: Safety and punt returner, NFL (five seasons)

A seventh-round draft choice of the Bears in 1981, Fisher played in 49 games on defense in four seasons. He intercepted five passes, forced nine fumbles and returned 120 punts for a 9.4-yard average over that period. After suffering an ankle injury prior to the 1985 season, he transitioned into a role as a part-time coach for the legendary 1985 championship Bears team.

Something you might not know: Fisher was the fourth wheel in a USC defensive backfield that included Ronnie Lott, Dennis Smith and Joey Browner.

4. Mike Mularkey | Tennessee Titans

Peter Brouillet/USA TODAY Sports

Position, top level played: Tight end, NFL (nine seasons)

A ninth-round pick of the 49ers in 1983, Mularkey was your classic backup tight end whose blocking skills helped him carve out a decade. He caught 42 passes in six seasons for the Vikings before the Steelers signed him and incorporated him more into the passing game. Mularkey caught 54 passes in his first two seasons with the Steelers and retired after the 1991 season.

Something you might not know: Mularkey was recruited to the University of Florida as a quarterback before switching to tight end.

3. Ron Rivera | Carolina Panthers

Peter Brouillet/USA TODAY Sports

Position, top level played: Linebacker, NFL (nine seasons)

His career mirrored Jack Del Rio's as a hard-nosed linebacker. Rivera played in 149 NFL games with 62 starts, including the playoffs, all with the Bears. A second-round draft pick in 1984, Rivera totaled 392 tackles and nine interceptions in his nine seasons. He was a reserve on the Bears' Super Bowl XX-winning team in 1985. At Cal, he was an All-American and totaled 13 sacks in 1983.

Something you might not know: Rivera still holds the University of California record for tackles behind the line of scrimmage in a single season: 26.5 in 1983.

2. Todd Bowles | New York Jets

Michael Zagaris/Getty Images

Position, top level played: Safety, NFL (eight seasons)

Bowles made the Redskins' roster as an undrafted rookie in 1986 and went on to play in 117 games, 82 of them starts, for both Washington and the 49ers. He was a starter with the Redskins' Super Bowl XXII championship team, gained a reputation as a smart signal-caller on a defense filled with household names and finished his career with 15 interceptions.

Something you might not know: Bowles dislocated six bones in his left wrist in August 1985, a month before his senior season at Temple. He still played in 11 games.

1. Jack Del Rio | Oakland Raiders

Malcolm Emmons/USA TODAY Sports

Position, top level played: Linebacker, NFL (11 seasons)

He patched together a fulfilling career as a do-anything linebacker, special-teams player and on-field leader. Del Rio appeared in 160 NFL games, with 128 starts, and totaled 941 tackles with the Saints, Chiefs, Cowboys and Vikings. He made the NFL All-Rookie team in 1985 as a third-round draft pick, was a two-time All-Pac-10 player at USC and is a member of the USC Hall of Fame.

Something you might not know: Del Rio is the only active head coach to be named to a Pro Bowl as a player, in 1994 while with the Vikings.