All NFL head coaches aspire and a small few achieve the ultimate football prize of a Vince Lombardi Trophy, but like everyone else, they have feet of clay. The high-stakes pressure to win often creates chronic stress that is detrimental to their health. Gary Kubiak became the league’s latest casualty to the unforgiving lifestyle expected of coaches as he relinquished the coaching helm of the Denver Broncos on Monday.

At his retirement news conference at club’s UCHealth Training Facility, Kubiak made the following statement:

Coaching is a very demanding business, it’s a tough business. I’ve been a head coach for 10 years. Each of us as coaches can sit up here and they could probably tell you that same thing I’m telling you. We all have a routine. I’ve always taken a lot of pride in coaching a football team, being there for the players, being there for the coaches, being there for the organization, doing a game plan and calling some plays on Sunday. This year I haven’t been able to do that. It’s been tough. For the first time, I’ve had to tell myself, ‘Hey, you can’t do that anymore.’ I just feel like it’s time for me to do something different. I’m retiring from coaching.

Kubiak joins a long list of highly successful NFL coaches who have left the league for health reasons. The Broncos are over represented on this list. Perhaps one of many reasons is the impact of high altitude pulmonary edema. The list starts with the namesake of the NFL championship trophy.

1. Vince Lombardi, Washington Redskins, 1970, age 57. As early as 1967 between his two Super Bowl victories, Lombardi complained about digestive problems. He retired from coaching the Green Bay Packers after winning the first two Super Bowls. Lombardi resumed coaching with the Redskins. But in 1970 he was diagnosed with colon cancer and died only weeks later.

2. Don McCafferty, Detroit Lions, 1974, age 53. McCafferty led the Baltimore Colts to victory in Super Bowl V. However, while doing yard work just before his first Lions training camp in 1974, he had a sudden heart attack and died very shortly afterward.

3. Mike Ditka, Chicago Bears, 1988, age 49. Two years after winning Super Bowl XX, Ditka suffered a mild heart attack during the 1988 season. He missed only one week before turning to coaching duties. Ditka continued to coach the Bears through the 1992 season but he never lead the Bears back to the Super Bowl.

4. Dan Reeves, Denver Broncos, 1990, age 46 and Atlanta Falcons, 1998, age 54. Reeves started to have chest pains before the start of the 1990 season, missing only one preseason game due to an artery-cleaning procedure. As the Falcons head coach in 1998, Reeves underwent quadruple-bypass heart surgery. Absent only two games, he led the Falcons to an NFC Championship.

5. Bill Parcells, 1992, age 50. Parcells had heart-bypass surgery during a coaching hiatus after winning the Super Bowl with the New York Giants before heading the New England Patriots. He later coached the New York Jets. Parcells never returned to the Super Bowl.

6. Joe Gibbs, Washington Redskins, 2005, age 64: During his second term as head coach of the Redskins, Gibbs had a stent inserted in a clogged artery. During his first term, Gibbs won three Super Bowls. But his second time around as coach the Redskins was limited to only one playoff game victory.

7. Chuck Pagano, Indianapolis Colts, 2012, age 51: Pagano was diagnosed with acute promyelocytic leukemia. In September he took an indefinite leave with Bruce Arians serving as interim head coach. By December, Pagano recovered well enough to resume his head coaching duties. Afterward he led the Colts to three consecutive playoff trips. But the last two seasons have both ended with 8-8 win-loss records.

8. John Fox, Denver Broncos, 2013, age 58. During the Broncos bye week, Fox felt light headed while playing golf in North Carolina. He was taken to a Charlotte hospital on Nov. 2 and had aortic valve replacement surgery. Defensive coordinator Jack Del Rio substituted for Fox during the next four Broncos games. Resuming his job, Fox led the club to its seventh Super Bowl appearance, losing to the Seattle Seahawks, 43-8. He coached one more season before he was replaced by Kubiak. For the past two years, Fox has coached the Chicago Bears to two losing seasons.

9. Gary Kubiak, Houston Texans, 2013 age 53, and Denver Broncos, 2016, age 55. In 2013 during a game against the Colts on Nov. 3, Kubiak collapsed along a sideline during half time. He suffered from a mini-stroke called transient ischemic attack and was taken by ambulance for hospital treatment. Defensive coordinator Wade Phillips became interim head coach. On Dec. 6 of that year, Kubiak was permanently removed by the Texans with three games remaining in the 2013 season. His season record was 2-11. In 2016 after a Broncos loss against the Falcons on Oct. 10, he was transported to a Denver hospital to treat a complex migraine. He missed the following Thursday night game against the San Diego Chargers. Before the Falcons game the Broncos had a 4-0 win-loss record. Including the Falcons game and afterward their record was 5-7.

10. Bill Belichick, New England Patriots, 2014, age 61. Consistent with his usual secrecy, Belichick did not disclose the cause of a health event. After the 2014 regular season finale loss to the Buffalo Bills, he was taken to the training room in Gillette Stadium for medical treatment. Nevertheless Belichick led the Patriot to win Super Bowl XLIX.

11. Bruce Arians, Arizona Cardinals, 2016, age 64. After Arians’ successful tour as Colts interim head coach, he became the permanent coach for the Cardinals. He led the club to an NFC championship game appearance. But in 2016 he was hospitalized in San Diego after experiencing stomach pains and hospitalized again in Arizona after incurring chest pains. Arians said at the time, “I’m too old not to listen to doctors anymore. I have a tendency to push it . . . but it’s nothing serious.”

Of note was Bear Bryant, who led the University of Alabama football team to six national championships. A long-time alcoholic, Bryant died of a heart attack at age 69, just weeks after retiring in 1983.

The coaching daily grind is brutal, as documented by ESPN’s Kevin Van Valkenburg when he tracked Baltimore Raven’s coach John Harbaugh for a week. It is no exaggeration to say that Harbaugh spent 100 hours working that typical week of an NFL season. To save time Harbaugh often slept in his office.

Another coach also had a reputation of skipping sleeping in his bed at home. Former Philadelphia Eagles coach Dick Vermeil would periodically check in local hotels with his assistants to gain more preparation hours. The brutal work schedule took its toll. Thirty-three years ago, Dick Vermeil resigned from the job because he burned out. He stayed away from coaching for 15 years before heading the St. Louis Rams in 1997. In his third season, he led the Rams to win Super Bowl XXXIV.

Another Super Bowl-winning coach, Jimmy Johnson, also claimed burn out when he left coach for good after the 1999 season. Bobby Ross did not wait for the end of a season to quit when he left the Detroit Lions with several games left in 2000. Vermeil told ESPN, “[A head coach is] like an engine. You can blow up a Porsche if you drive it too hard, and a football coach is no different. You have to find a way to turn it off.”

Coaches’ families go through stress as well. For coaches to progress in their profession, frequent moves are a necessary cost. Kubiak had seven different coaching jobs over 24 years. Wade Phillips had 14 different instances of moving during a coaching span of 37 years. Arians has moved 13 times over 31 years.

Part of a head coach’s job is to help players’ cope with their personal problems. For three seasons Parcells helped star linebacker Lawrence Taylor walk the tightrope by staying off illicit drugs. Taylor had two strikes against him under the NFL substance abuse policy. Another drug violation carried a league suspension against Taylor, who led the Giants to win Super Bowl XXV. Parcells soon left the Giants for health reasons, subsequently having heart surgery. Chiefs coach Romeo Crennel was less successful. After pleading with linebacker Jovan Belcher, the player nevertheless committed suicide. Crennel was the Chiefs head coach for only two years in 2011-12.

Head coaches are the gatekeepers for football players to achieve their dreams of competing in the NFL. Firing subordinates can be a high stressor. It is a necessary part of the job for coaches to let go of more than 50 players per season. There is typically a 40 percent turnover of active roster players per season.

Coaches are held accountable by NFL owners to the impossible standard that season outcomes are firmly under the coaches’ control. Four or fewer plays often determine winning or losing a game, and frequently dictate if a team gets the top playoff seed or even making the playoffs at all. A questionable official’s call, a tip of a ball, a split-second loose grip, or an errant eye glance are common game changers.

With annual player payrolls now exceeding $160 million and club values typically reaching $2 billion, every NFL team has become a big operation. During the regular season, a head coach oversees a floating village of players, coaches, trainers, staff, and families – traveling among nine cities.

Pro football players see the coaching grind firsthand. Perhaps that is a contributing reason for why there are so few head coaches who are also former NFL players. For instance, Belichick played NCAA Division III football for Wesleyan University. Former quarterback Billy Kilmer was asked if he ever wanted to coach. His reply: “No way. I don’t want to spend 15 hours a day in a 10′-by-13′ cell.”

Hall of Fame linebacker Kevin Greene transitioned to become a linebackers coach for the Green Bay Packers. In spite of his love for the game and players and coaches, he left the Packers to spend time with his teenage son, including coaching him in high school football. Bill Cowher and Jon Gruden have stayed in television broadcasting in spite of several offers to attempt repeating their Super Bowl victories.

Since the NFL-AFL merger in 1970, the only NFL players to later win the Super Bowl as a head coach are Ditka, Dungy, and Kubiak. In contrast the majority of MLB managers and NHL coaches have played in their respective leagues. About half of the NBA coaches are former league players.

Good habits of diet and exercise can be undone by relentlessly intense stress. Health guru Pete Carroll, coach of the Seattle Seahawks, promotes positive thinking and better living habits like sleep. At age 65, his third stint as an NFL coach continues to be successful, including a Super Bowl win.

Broncos general manager John Elway is acutely and personally aware of the toll a coach’s lifestyle has on health. During his playing days as a Hall of Fame quarterback he began to acquire car dealerships. Elway was bought out by AutoNation for $82.5 million in 2001 in a mostly stock deal. He used his idle time to spend a month with his father Jack Elway who, as Broncos head pro scout, prepared for that year’s NFL draft. Just before the draft, Elway’s father died of an apparent heart attack on April 15, 2001. He was 69. Prior to scouting for the Broncos, Jack Elway coached football for 37 years.

In Denver’s Monday news conference, Elway stated the following:

It’s with mixed emotions [that I accept Gary Kubiak’s retirement], but in the long run, it’s the right thing for Gary. I think that’s the most important thing. When he said, ‘I want to talk to you as a friend,’ Gary personally became the priority. I can’t tell you how many times I thought about putting my boss hat back on and putting my selling process back in there and see what we could do to try to make it work. [But] Gary . . . knew what was right for him.

Sometimes the best decision an NFL coach can make is walking away.