It’s fair to say the most important factor in an NFL coach’s success is the ability of his quarterback. It’s no coincidence this winter’s top candidate, Seahawks defensive coordinator Dan Quinn, was willing to pass on other opportunities once the Falcons job became available. The Falcons may have a bruised, top-heavy roster, but Matt Ryan is one of the 10 best quarterbacks in the league. Likewise, while Colts general manager Ryan Grigson has made plenty of major missteps during his time at the helm, inheriting the first overall pick in a draft with Andrew Luck in it covers up a lot of those mistakes.

More 2015 NFL Preview It's almost here. For everything you need to know about the new season, follow all of Grantland's coverage. Team Predictions: The Contenders

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The NFL 100 Rankings, Part 1

The NFL 100 Rankings, Part 2

All of our NFL preview coverage! This came up the other day when I was writing about Lovie Smith and the Buccaneers, since it’s apparently my turn to rep for Grantland’s endless love affair with Tampa Bay. I’m not sure how good Jameis Winston will be, but it occurred to me that the first overall selection in this year’s draft is very likely to be the best quarterback Smith has ever had. And in looking back at the Rex Grossmans and Josh McCowns, I started to wonder: Has Lovie Smith had the worst crop of quarterbacks of any head coach in league history?

Of course, there are a million ways to answer this question. As middling as Grossman and Kyle Orton were, they were a damn sight better than the Joey Harrington–Chris Redman–Byron Leftwich troika that Bobby Petrino had to endure during his 13-game run in Atlanta. Part of judging the worst here is average performance, but a lot of it boils down to longevity; it’s extremely impressive for a head coach to last 10 years with bad quarterbacks. There’s a quantitative process behind this, of course, but there’s also inevitably going to be some qualitative comparisons between coaches with bad quarterbacks in terms of intensity and longevity.

Feel free to skip the next section if you just want the answers. Let’s get to work.

Joe Robbins/Getty Images

The Method

To estimate the typical quarterback play each coach dealt with, I tracked every team since the AFL-NFL merger season of 1970. Our measure of quarterback play is adjusted net yards per attempt, which is a reasonably effective metric for the impossible task of capturing everything about quarterback play in one formula. This one is better weighted than passer rating and includes sack yardage.

To compare data across the drastically different passing eras of the last five decades, I expressed the numbers relative to the average adjusted net yards per attempt in the league each season. In 2014, that was 6.14 ANY/A. The Packers averaged 8.39 ANY/A and were a league-best 36.8 percent above average, while Blake Bortles led the Jaguars to a league-low 3.97 ANY/A, coming in 35.4 percent below league average. We’ll express these numbers as percentages relative to the mean from here on out.

Unfortunately, I don’t have game-by-game data linking each coach to the games in which he was running the team. That’s not a problem with full seasons, but during those years when a squad went through one or more coaches, there’s no easy method to assign the appropriate percentage of the performance to each coach. The simplest way was to assign a proportional amount of the overall seasonal performance to each coach and factor it in as a partial season. (Again, the best candidate for this is going to be someone who coaches for a long time with really bad quarterbacks.)

Finally, I looked exclusively at coaches who lasted 70 games or more. That’s five full seasons under the 14-game schedule, when teams seemed to be a little less aggressive about firing their head coaches, and it’s four-plus seasons under the 16-game calendar. If you make it that far with terrible quarterback play, you’re doing something right.

With those numbers in mind, let’s examine the 10 coaches who have been saddled with the worst quarterback play since the merger. Eight made it through two jobs, with a ninth set to start his second gig with another batch of dismal prospects. (You can probably guess who that is.) For each, I’ll include his run in the league and the primary quarterbacks he was cursed to work with. Sorry, Carolina. You’re up first.

The Candidates

10. Dom Capers: 15.4 percent ANY/A below league average

Teams: Carolina Panthers (1995-98), Houston Texans (2002-05)

Notable Quarterbacks: Kerry Collins, David Carr

Ah, the curse of expansion franchises! Capers spent his entire head-coaching career with two highly drafted young quarterbacks, neither of whom turned out to be very useful. Collins had a Pro Bowl run in his second season, but he was well below average in 1995 and 1997 thanks to a nasty interception habit. By the time Steve Beuerlein took over for a publicly shamed Collins in 1998, Capers was already on his way out the door. And with his second chance, Capers’s Texans simply failed to protect the first overall pick, with Carr leading the league in sacks taken during three of his four seasons.

9. Rich Kotite: 16.1 percent ANY/A below league average

Teams: Philadelphia Eagles (1991-94), New York Jets (1995-96)

Notable Quarterbacks: Randall Cunningham, Jim McMahon, Bubby Brister, Boomer Esiason, Neil O’Donnell, Frank Reich

It’s fair to say Kotite is one of the least-loved skippers in league history, in no small part thanks to his ill-conceived decision to coach teams with two of the league’s most pessimistic fan bases. It’s also fair to say Kotite didn’t get much help. His worst year came in 1995, when Esiason and Brister were 38.8 percent below league average. That Jets team averaged a lowly 3.3 net yards per attempt, and the only squad within a half-yard per attempt was Kotite’s old charges in Philadelphia. After a free-agent move for O’Donnell failed to deliver, Kotite left New York and never returned to coaching at any level.

8. Bum Phillips: 17.0 percent ANY/A below league average

Teams: Houston Oilers (1975-80), New Orleans Saints (1981-85)

Primary Quarterbacks: Dan Pastorini, Kenny Stabler, Archie Manning, Richard Todd

Blame Phillips’s time with the Saints. His Oilers teams posted an average ANY/A that was 6.9 percent below league average. That and Earl Campbell were enough to win a whole bunch of football games — and Phillips went 55-35 in Houston before being fired after an 11-5 season in 1980. His Saints teams weren’t quite as impressive, going 27-42, and the passing game was at the root of those problems. During Phillips’s five years in New Orleans, the Saints posted five consecutive seasons with an ANY/A that was 20 percent worse than league average.

Thearon W. Henderson/Getty Images

7. Romeo Crennel: 19.1 percent ANY/A below league average

Teams: Cleveland Browns (2005-08), Kansas City Chiefs (2011-12)

Notable Quarterbacks: Trent Dilfer, Charlie Frye, Derek Anderson, Brady Quinn, Matt Cassel

Crennel’s charges delivered exactly one impressive season, that miraculous 2007 Pro Bowl campaign from Anderson in Cleveland. Here are Anderson’s numbers from that year and over the remainder of his career:

Year Cmp Att Cmp% Yards Y/Att TD INT 2007 298 527 56.5% 3,787 7.2 29 19 Elsewhere 527 1,010 52.2% 6,120 6.1 29 36

There’s more on those Anderson-Quinn Browns teams coming up.

6. Ray Perkins: 19.2 percent ANY/A below league average

Teams: New York Giants (1979-82), Tampa Bay Buccaneers (1987-90)

Notable Quarterbacks: Phil Simms, Vinny Testaverde

It’s disappointing when you take two longtime starters and fail to find success, but that’s exactly what happened to Perkins. He took over as Giants coach and drafted Simms in the first round in 1979, but Simms never really broke through during Perkins’s four-year run with the team. Simms produced two middling years before giving way to Scott Brunner during the 1981 playoffs and 1982 regular season.

Perkins then left for Alabama. (His replacement was Bill Parcells, who chose Brunner before eventually transitioning back to Simms.) When Perkins made his way back to the pros, he took over a Bucs team with the first overall pick in the upcoming draft and a failed quarterback of the future. He traded the quarterback to the 49ers and used the pick on Testaverde, who threw 35 interceptions in his first full season. The quarterback Perkins traded, of course, was Steve Young.

5. John McKay: 19.6 percent ANY/A below league average

Teams: Tampa Bay Buccaneers (1976-84)

Notable Quarterbacks: Steve Spurrier, Gary Huff, Doug Williams, Jack Thompson, Steve DeBerg

Behold, the worst passing season (per ANY/A) since the merger, courtesy of the 1977 Buccaneers:

Player Cmp Att Cmp% Yds TD INT Y/Att ANY/A Rating Gary Huff 67 138 48.6% 889 3 13 6.4 1.40 37.4 Randy Hedberg 25 90 27.8% 244 0 10 2.7 -3.21 0.0 Jeb Blount 37 89 41.6% 522 0 7 5.9 0.40 28.4 Louis Carter 0 2 0.0% 0 0 0 0 0.00 39.6 Dave Green 2 2 100.0% 59 0 0 29.5 29.50 118.7 Totals 131 321 40.8% 1,714 3 30 5.3 -0.06 22.5

You’re not reading that incorrectly. The Buccaneers actually posted a negative ANY/A. They would have been better off immediately taking the snap and spiking the football across their 369 dropbacks. If you’re wondering why they didn’t give Dave Green more reps at quarterback, it’s because he was the punter. Randy Hedberg and Jeb Blount never played again, and Hedberg, as you can probably guess, has the worst passer rating in NFL history. This sorry group combined for an ANY/A that was 101.6 percent below league average in 1977.

4. Eric Mangini: 19.8 percent ANY/A below league average

Teams: New York Jets (2006-08), Cleveland Browns (2009-10)

Notable Quarterbacks: Chad Pennington, Brett Favre, Derek Anderson, Brady Quinn, Colt McCoy, Jake Delhomme

That’s not a bad group! It’s hard to really compare a lineup with a certain Hall of Famer (Favre) and an above-average passer when healthy (Pennington) to some of the other combinations on this list, but Mangini didn’t often see the best of his quarterbacks. Favre was acquired in early August, which was way too late for him to grow comfortable with a new playbook, and he was walking wounded by the end of his lone season in New York. Pennington broke down halfway through Mangini’s second season and gave way to inexperienced backup Kellen Clemens for eight starts. And whatever you want to say about that Cleveland combination is probably unsuitable for a Disney-owned website.

Streeter Lecka/Getty Images

3. Lovie Smith: 20.2 percent ANY/A below league average

Teams: Chicago Bears (2004-12), Tampa Bay Buccaneers (2014)

Notable Quarterbacks: Kyle Orton, Rex Grossman, Brian Griese, Jay Cutler, Josh McCown

Ah, the raison d’être comes up just short! A disastrously bad performance by McCown in 2014 (the Bucs were 21.2 percent below average) wasn’t enough to earn Smith a top-two spot. And, actually, that pales in comparison to the minus-45.4 percent mark posted by the Bears during his first season in charge, 2004, when Chad Hutchinson, Craig Krenzel, and Jonathan Quinn spent 13 games filling in for an injured Grossman.

During his 10 years as an NFL head coach, Smith has yet to have a single season when his quarterback posted an ANY/A better than league average. The only other coach to do that for as many seasons as Smith is Dick Jauron, who happened to be his predecessor in Chicago. Smith has had only one season when his quarterback managed to make it within 10 percent of league average — in 2006, when Grossman stayed healthy and the Bears made it to the Super Bowl. If Jameis Winston is just passable, it would be one of the best seasons a Lovie Smith quarterback has ever had.

2. Marion Campbell: 20.5 percent ANY/A below league average

Teams: Atlanta Falcons (1974-76), Philadelphia Eagles (1983-85), Atlanta Falcons (1987-89)

Notable Quarterbacks: Bob Lee, Steve Bartkowski, Ron Jaworski, Scott Campbell, Chris Miller

Marion Campbell held this title for the better part of the last 25 years, and he would still be no. 1 if we assigned him full credit for the 1974 Atlanta Falcons. The former Pro Bowler was serving as the team’s defensive coordinator before taking over as head coach for the final six games of the year for Norm Van Brocklin. Van Brocklin was a wonderful quarterback, but in his final season as a head coach, his passers put together one of the worst seasons in NFL history:

Player Cmp Att Cmp% Yards TD Int Int% Y/Att Rate Bob Lee 78 172 45.3 852 3 14 8.1 5.0 32.4 Pat Sullivan 48 105 45.7 556 1 8 7.6 5.3 33.7 Kim McQuilken 34 79 43.0 373 0 9 11.4 4.7 18.0 Totals 160 356 44.9% 1,781 4 31 8.7% 5.0 27.8

The resulting ANY/A figure was 100.5 percent below league average, trailing the aforementioned 1977 Bucs as the second-worst ANY/A since the merger. And McQuilken, who started seven games, is probably the worst quarterback in league history to see multiple years of action. His career adjusted yards per attempt is minus-0.33. That’s not a typo. Not only is McQuilken the worst passer since the merger in just about every rate statistic (minimum 200 pass attempts), in many cases, it’s not even very close:

Stat Career Rank (of 359) Next-Worst Yards/Attempt 4.2 359 4.7 INT% 10.7% 359 9.3% TD-to-INT Ratio 4-to-29 (0.14) 359 2-to-13 (0.15) Passer Rating 17.9 359 32.6 AY/A -0.33 359 1.82

1. Rex Ryan: 21.2 percent ANY/A below league average

Teams: New York Jets (2009-14)

Notable Quarterbacks: Mark Sanchez, Geno Smith

You already know all about everyone involved in this blurb. The best season a quarterback has had under Ryan was in 2010, when Sanchez improved to an ANY/A that was 5 percent below league average. Otherwise, his quarterbacks have been remarkably, consistently dismal:

Year Primary QB Team ANY/A vs. League Avg Rank 2009 Mark Sanchez 3.96 -29.9% 27 2010 Mark Sanchez 5.45 -5.0% 21 2011 Mark Sanchez 5.12 -13.2% 20 2012 Mark Sanchez 4.29 -27.7% 30 2013 Geno Smith 4.18 -28.9% 32 2014 Geno Smith 4.75 -22.5% 30

And while hope springs up around the league in August, there’s little reason to think the combination of EJ Manuel, Matt Cassel, and Tyrod Taylor will improve things for Ryan in Buffalo. They’ve been surprisingly effective in the preseason, but almost everyone looks better against vanilla defenses. The dark truth remains: Ryan will likely still be no. 1 on this list if we run these numbers again next year.