How about I let Coach Marrone explain it to you:
"The problem I have is again a lot of it is how he comes back and again there goes the variable thing, when he comes back, did he miss time? No one ever really start off where they left off."
In other words, he will need time after he returns to get back into form. So if he can't practice until the week of the Pats game then how can he possibly be ready by game time?