Haha, ......easy?
A good player will recognize man defense right away and rip it up. I play with bama. If you go man on me julio jones is wide open for posts as soon as he gets the inside. One mlb can't cover all crossing routes.
The correct answer to stopping 5 wide is to mix zone coverages along with some blitzes. Switch up your defenses and looks. This, however, is not the answer. Yeah, mix in some man, but I consider myself a pretty decent player, and I can tell you that i'll recognize man right away and check down to the player who's running the most man friendly route.
Use defensive keys to shift coverage, or focus on one receiver. Shift your safeties in if you're getting beat on posts, yatta yatta....