Just ask Jason Kelce and Todd Herremans, both of whom suffered major injuries.
Kelce has had a rough road after tearing the MCL and ACL in his knee during week two.
"This isn't just a game that you're messing with. Every single day just walking around, trying to go up a flight of stairs. You're sidelined from life for a few weeks or months in a lot of cases" said Kelce.
Herremans spent five weeks on a scooter after dislocating a bone in his foot during week nine. It's a rare injury with a long recovery.
"I decided I'm not going to cut my hair until I'm 100 percent healthy, so I just have to keep it out of my eyes while I'm working out," said Herremans.
He should be able to cut his hair soon, he expects to be cleared to play in a couple of weeks. Kelce hopes to be back by May
In the meantime, the two are rehab buddies, working hard together to get back on the field.
"I was without a rehab partner for about five or six weeks then luckily Todd had a major injury so he had to join me," said Kelce.
Since Kelce and Herremans were injured, everything has changed but both say they like the vibe that Chip Kelly brings to the place.
They both know with a new coach, there will be an open competition for jobs. However these two have already been competing against each other all rehab long.
"We'd see who can grow out longer hair, bench press too," said Kelce.
"It makes the days go by faster, it's fun" said Herremans.