If you were a football coach, you could just say someone was hurt. Some coaches do this because they know being hurt can be a pretty obvious thing, and even if you camouflage it and pretend like someone isn't, a smart enough team will force you into subbing for the injured person really, really quickly. The cornerback who winces when he runs? You are throwing at that person until they are taken off the field for an able body.
Then again, you could be like Will Muschamp. Muschamp comes from the ACL CONFIDENTIAL school of coaching, the one where each piece of injury news is a shiny nickel you do not want to just toss into the opposition's coffers. The upside is that you may be able to gain a momentary advantage, conceal an injury, and make your opponent prepare for two different things at the same time. That's the argument, at least, and some very smart football coaches like Bill Belichick make a lot of money thinking exactly like this.
The downside: having everyone freak out about a possible injury, and then watching a player's mother embarrass you by breaking injury news for you because you won't talk to the media unless you really, really have to. If you have any other questions, please direct them to the press release "Florida Football 2012: Where ██████████ and ███████ meet █████████ and make █████████████."*
*The Florida SID. Please tell us what this person does on a daily basis besides not answer phones.