Bryton Barr is a 23-year-old linebacker who started his college football career at Towson in 2012. The UMass transfer can finish his career in 2018. Barr petitioned the NCAA for two years of extra eligibility and got both of them, PennLive reports.

If things go the way they’re supposed to go, a Division I athlete shows up on campus and a five-year clock starts. The player gets five years to play in four competitive seasons, and once those five years are up, it’s time to leave. That clock isn’t extended if a player decides to transfer and needs to sit out a one-year eligibility waiting period.

But it’s possible to get more than five years, and it’s even possible to compete in more than four. There are multiple ways, but the simplest is to get hurt.

The medical hardship waiver is the most common tool to get extra years

Barr’s example is instructive. In 2012, he played a full season for Towson. In 2013, he tore a pectoral muscle in the second game. He missed nine of the Tigers’ 11 games that season, then suffered pectoral and ACL tears in the run-ups to the next two seasons. Starr played a total of two games between 2013 and 2015.

When a player misses a season because he’s injured, his team can file a petition with the NCAA for an offsetting year of eligibility. Those requests are usually granted as long as the player didn’t participate in more than three games — or 30 percent of the scheduled games, whichever’s higher, in sports other than major college football.

Because Barr’s 2013 season ended after two games, he was well within hardship waiver range. His brief on-field appearance didn’t constitute a year of competition, and he got an extra year added to his clock.

A seventh year of eligibility is exceptionally rare, but Barr isn’t football’s first. Texas Tech offensive lineman Tony Morales got a seventh year granted, after missing four in a row with injuries. San Jose State running back Deontae Cooper did, too, after having three years erased by injuries. In the last decade, it’s also happened at Utah and Robert Morris. Some big-name players, like former Houston QB Case Keenum, have hit six.

Other than injures, a player has a few ways to get a waiver for extra years

The key here, according to the NCAA’s Division I manual, is that the player missed a season of competition because of something “beyond the control of the student-athlete or institution.” Aside from injury, that can be a few things:

A serious illness in a player’s family.

A player’s school giving him bad academic advice or guidance, which leads to that player becoming academically ineligible.

A natural disaster, like an earthquake or flood.

“Extreme financial difficulties” stemming from a major life event, in which the player or the person a player depends on for money suddenly can’t make it. The NCAA cites job layoffs and family deaths as examples of qualifying events.

Players still need to go to class in some fashion. A player in his seventh year isn’t still taking undergrad sociology, but the NCAA’s academic rules don’t stop applying.

How far could this go? It’s not exactly clear

I can’t find reports of a player getting more than seven years. Has it happened? Unclear, because the NCAA doesn’t keep a detailed public accounting of every waiver given to every player ever. But getting more than five years to move through a career is simple, if you’ve suffered some painful injuries.