September 10, 2026 — 3:53pmFrom head to toe, Nick Bosa catches your eye on the football field.The San Francisco defensive end has been a star dating back to his US college days at Ohio State and his rippling arm muscles and powerful legs capture plenty of attention, whether at training, on game days or even modelling underwear, as he did in 2023.San Francisco 49ers defensive lineman Nick Bosa runs on Wednesday.AP PhotoBut it’s Bosa’s quads that have earned him extra attention this week as he prepares to return to the field after recovering from a knee reconstruction last October. His right quad has suffered some muscle atrophy during his recovery and is now noticeably smaller than his left.That difference has lessened somewhat since he returned to full training, but it’s still stark for the $235 million ($US170 million) star who is contracted with the Niners until the end of the 2028 season.San Francisco linesman Nick Bosa stretches at AAMI Park on Wednesday.Luke Hemer“I don’t remember [the size difference], but it was drastic after surgery,” Bosa told The Athletic this week.“It’s going to take a couple of years to get that last couple of centimetres.”Niners coaches have made it clear this week that Bosa, 28, will be playing at the MCG on Friday morning, and he moved well during the portion of training that was open to the media on Tuesday and Wednesday.Niners defensive coordinator Raheem Morris has no issues sending his superstar into the centre of battle this week.“Nick Bosa is really easy. You watch this guy do it over a span, a long time in his career, [and he’s] been able to do it at different levels,” Morris said on Wednesday.“[It’s] a different question than what we just talked about with Romello [Height, another Niners defensive end], where we haven’t seen him do it yet.“Bosa knows his body as well as anybody.“He’ll be prepared and ready to go as well as anybody, whether it’s from a conversation in point, from meetings, from what he needs to get ready for his body. [I have a] very high confidence level in where he’s going to be.”Skims ambassadors: NBA star Shai Gilgeous-Alexander, NFL lineman Nick Bosa and Brazilian soccer player Neymar Jr model underwear in 2023.Quad muscle atrophy is particularly common for those who’ve suffered ACL ruptures, given the need for the leg to be immobilised in the weeks after surgery.In sports where athletes do more running or constant aerobic activity, like Australian rules or basketball, athletes typically regain a good amount of their muscle by the time they return to action.But sometimes photos emerge of how players look in their return to training.Bayern Munich and Canada soccer star Alphonso Davies was shown running five months after his knee reconstruction last year.His right quad was wafer thin while his left was noticeably larger, which caused a stir, given fans of both the European powerhouse and his national team were desperate for him to return to full fitness.Physiotherapist Konstantinos Ikonomou highlighted the issues around quad atrophy in a Linkedin article referencing Davies’ issues last year, explaining that most rapid muscle loss happened in the two weeks after surgery but could continue for weeks or even months after.“This isn’t unusual. Quadriceps atrophy is one of the most stubborn challenges after ACL reconstruction – even in elite athletes with world-class rehab teams,” Ikonomou wrote.A number of NFL stars, such as Detroit defensive ace Aidan Hutchinson and Washington wide receiver Stefon Diggs, have featured in training videos on social media that have highlighted the same issue.From our partners