I think the more natural answer is Can't. After all a person who can't is more likely to need showing that someone who can. But like so many of the these questions, can is not out of the question. Some people like being ironic.
Can - will mean a question about if he can play football.
Can't - is a surprise about that he can't play; or about a guess that he can't. Or asking for a reason for something that makes one doubt taht he can play.
- Can you play footbal? If you can, we could use another forward in our team.
- We are going to play football. Are you coming with us?
- Can't you play? or are you simply not interested?