I'd play with it, but I'd take one thing in consideration which is the person I'm playing. I'd let them know that I'm sick with the flu but I'm trying to play through it(assuming these are pick up matches). If they have no problem with it, I'd play through it. I think it helps me to play through it. If we stopped playing everytime we were not 100 percent most of us would never get to play. I've always got something sore on me. I'm 44 so I've just come to understand I'll do what I can to keep the soreness away but I won't stop playing everytime that I'm not 100 percent. I say as long as the other person is cool with it...roll with it.