QB Troy Smith
Troy was named the starter following Alex Smith's poor performance against the San Diego Chargers. Despite the fact that the Chargers have made three great quarterbacks look bad this season, Troy is the guy as the 49ers head to St. Louis, and he's probably not a great option for fantasy football. If he doesn't play well, he can be pulled at the first sign of collapse. If he's playing well, it's probably in spurts, and the 49ers will likely run the ball.
Sit Troy Smith
RB Brian Westbook/Anthony Dixon
The 49ers will be running the ball, but it's a toss-up as to which of these players you should be starting, if either of them should be at all. Antony Dixon will probably get more carries, but he's a little banged up. It's hard to recommend either of these guys.
Sit Brian Westbrook/Anthony Dixon
TE Vernon Davis
Davis is probably due for another big game, perhaps a big touchdown. He had one of over 70 yards the last time he played in St. Louis, and he'll likely be Troy's primary target. Davis could have a big game, with or without Troy having one of his own.
Start Vernon Davis
WR Michael Crabtree
Crabtree, at this point, is not a starting option. It's possible he breaks out and has a good game, and that's actually the gut feeling at the moment; but it's not smart right now.
Sit Michael Crabtree
WR Josh Morgan
We're going to go ahead and buy into the hype and say that Mike Singletary gets his first win with a 49ers receiver having 100+ yards (presently 0-8 in that regard). Morgan will have a big game to help the 49ers get where they need to be. He's a solid option in deeper leagues.
Start Josh Morgan
This game will either be really low scoring, or very high scoring. The 49ers defense is a solid option in that regard, but it's a definite "owners beware" moment.
Sit 49ers Defense