EDSBS has posted a fine rebuttal to the question every Captain Obvious has asked: "You know, is gonna get hurt, and then where will Michigan be?"
The question applies so universally that it has no specific value. Plug it in with any player: "What ifgets hurt?" (Answer: "They'll play the next incarnation of behind him.") "What if gets hurt, and then where will Florida be?" (Answer: "We'll just give up on the pass game entirely and bypass those frustrating drops on four yard hitches called on 3rd and 5," that's what we'll do.) "What if Jordan Jefferson gets hurt?" Well, LSU will probably play Jarrett Lee, and then really spectacular things start happening.
Yes, Michigan might be in trouble if Denard goes down. Just like every other team would be in trouble if they lost their best player.