Nick Bosa was looking sharp when the San Francisco 49ers began training camp. It was like he never tore his ACL last year, as Trent Williams put it.However, since Aug. 5, Bosa has been missing in action. There wasn't a thorough explanation given for his absence until Kyle Shanahan spoke at a press conference for the first time on Saturday."He was doing great, and then he got sore just going through some of the individual," Shanahan said. "You wish that didn't happen, but no, there's no concern to where something's happened that is a big setback or anything. We'll wait until the soreness goes away and evaluate why the soreness has happened, but I still feel pretty good about that.”Soreness seems to fit the bill. Training camp is the hardest time Bosa gets to push himself, but he's now missed a fourth straight practice. He wasn't seen on the practice field on Monday, which is alarming.49ers fans should be concernedAug 3, 2026; San Francisco, CA, USA; San Francisco 49ers defensive end Nick Bosa (97) during training camp at Levi's Stadium. Mandatory Credit: Sergio Estrada-Imagn Images | IMAGN IMAGES via Reuters ConnectThis should make 49ers fans concerned. I don't believe it's as simple as "soreness" for Bosa. Why would he be a ghost if it were soreness? Is his condition worse? That wouldn't be out of the realm of possibility. It happened to Ricky Pearsall two weeks ago. He thought he was fine in the offseason until he pushed himself at camp.It could be that Bosa is dealing with more than what Shanahan let on. Or, Bosa's absence could be tied to his contract. This isn't anything new to him.Bosa's current deal expires after the 2028 season. That typically would leave zero chance of a contract holdout. However, there is a potential out in Bosa's deal after this season.Bosa is too smart with his contracts and money. He could easily see that as a chance to challenge the 49ers for more security.And now that he's shown how normal he looks after some practices, he can use that as evidence to the 49ers that his torn ACL shouldn't be a concern to them."Look at me out there. I'm still an elite player. It's not a worry. Pay me."That's the message being sent if his absence is, in fact, related to a contract dispute. I wouldn't put it past Bosa. Other than Brandon Aiyuk, he was their biggest headache for negotiations.Could he be delivering another to the 49ers now? His fourth straight missed practice could indicate that, and it shouldn't be downplayed.Follow Jose on X (Twitter) @JS3sanchezz and his YouTube channel to interact with him on the 49ers and more.Add us as a preferred source on GoogleFollow