With the #1 pick in the round, 4th is probably too high. There will be some legitimate starting caliber players to be found on the O and D lines there.
I'd use our 5th on him and install him as a NCB/Returner.
He'd essentially be what Javier Arenas was supposed to be, only he'd actually be a premier returner and he'd be taken in the round you're supposed to take guys like that.
Lattimore, OTOH, I'd strongly consider in the 4th. I know it's risky, but man medicine does some amazing stuff. He could be an amazing runner and it sure would be nice to have him in the pipe for the 2014 season.
If McGahee went in the first, Lattimore will probably go in the 2nd.
If you can't draw a crowd, draw dicks on the wall.