That's a point I've made elsewhere. For a 4th, you should get a guy you know can play, not a pig in a poke. If Lance had looked great at the NFL level but was simply snakebit by injuries, I'd feel differently.
This has been a problem for years. Underpowered guys who get pushed around. It's usually the reason why we seldom win exhibition games because the backup offense can get nothing going. Pray for good health on the line this year because some of these guys might have to play.