Bosa says he rarely takes them off, other than to put his Nike Jordan cleats on for practice.
That's right, Bosa is coming after your Birkenstocks.
"I wear these things everywhere because I've never put anything on my foot that forms and fits better to my arch," Bosa said. "I don't take them off, they really mold to your foot."
"I'm trying to convince him to get us all Birkenstocks for Christmas," fellow defensive end Isaac Rochell said. "He wore them all camp, and has worn them all season in the facility."
Joey Birkenstocks? When Bosa isn't crushing QBs, he likes to lounge around in these comfortable shoes that fit his feet like a glove. "I don't take them off, they really mold to my feet," Bosa said. H/T master iPhone picture taker @GManzano24 pic.twitter.com/xoLs6DGbb8— Eric Williams (@eric_d_williams) December 20, 2019
Footwear is an important topic of conversation in NFL locker rooms in general, and specifically for Bosa after he suffered a bruised left foot last year during training camp that forced him to miss the first nine games of the regular season.
Bosa's teammate, safety Derwin James, went through a similar ordeal this year. James suffered a Jones stress fracture of the fifth metatarsal of his right foot during a joint practice against the New Orleans Saints on Aug. 15. The injury was a refracture of an initial stress injury he suffered heading into his sophomore season at Florida State.
Foot specialist Dr. Robert Anderson performed surgery to repair the issue on Aug. 22 in Green Bay, Wisconsin. Anderson also treated Bosa for his foot issue.
The Chargers placed James on the injured reserve to start the season, forcing him to miss the first 11 games.
The two foot injuries are examples of a leaguewide rise of lower-leg injuries over the past 10 years, according to data collected annually by the league's foot and ankle committee.
Bosa said his injury forced him to rethink what he wore on his feet on game days.
"When the injury happened, you're obviously going to research and look at everything you can," Bosa said. "That was one of the first things the doctor said, is start with what shoes you are wearing.
"So that injury certainly gave me an appreciation for floors and walking around on different surfaces, and the impact that it can have on your body, like walking around on hard concrete. I would be walking on carpet, and then take one step off onto concrete and my foot would kill me. So it just kind of showed me how important footwear is, not just cleats but wearing it every day."
ESPN injury analyst and licensed physical therapist Stephania Bell said the goal of the foot and ankle committee, headed up by Anderson, is to create player awareness about things they can do to mitigate some of the injury risk for foot and ankle issues. That includes properly fitted footwear.
"Look, if that wasn't a thing, players wouldn't have all of these shoe deals, right?" Bell said about players wanting good-looking cleats. "It's about how 'fresh' their kicks look, if I can borrow the lingo of the kids. That's what it's always been about, and if you think about it, growing up that's what they saw. So that's really embedded in the culture of sports.
"Now, that's not bad. But there has to be some balance because this is a piece of equipment, much like the helmet and shoulder pads are pieces of equipment."
All 32 teams have 3D scanning systems to accurately measure players' feet and help determine the best footwear for each player. The league and the NFL Players Association also collaborate on helping players determine what footwear they should use in practice and on game days, including the use of shoe-testing machines to evaluate the best cleats to use on specific surfaces.
"You start adding up the time lost among these players and it's every position," Bell said. "It's guys on the line, as well as defensive backs and wide receivers. It can be anybody, really.
"So it affects everyone, the numbers are up and they are really trying to figure out what's the best point of attack. It's going to be multipronged, but this educational piece is one part of it."
Count James as one of those kids interested in cleats that made him look good.
"I was always the guy growing up who wanted the best-looking cleats, no matter how they felt," James said. “For me, I like a loud color. So if it's between yellow and blue, I like the yellow. When I went to the store, I wanted the best-looking one, even if I couldn't fit in them I was trying to put them on. They had to be fire.
"Now, with the foot injury I have to go more for what's comfortable and safe for my foot. So I know I have to go with a different style, a different flavor."
Bosa signed an endorsement deal with Adidas as a rookie. However, during offseason work this year, he tried teammate Melvin Ingram's Jordan Brand Nike cleats, and after a couple of months of using them, Bosa adopted those shoes as his own.
After his deal was up with Adidas, Bosa signed with Nike.
"I don't think it's about one brand or another," Bosa said. "It's about having something that can form to your foot with a wide enough base to support it."
James has stayed with Adidas, finding a sturdier, comfortable shoe that provides him good support.
"I love Adidas," James said. "I can always call them for anything I feel like. I don't really have an issue with them."
Rochell is endorsed by Under Armour, and has worn that brand of cleats since college at Notre Dame. Rochell said he's spoken to Bosa about his choice of footwear for football.
"I think it's about wearing what's comfortable," Rochell said.