The following is the fifth in a series of weekly stories on MLB.com examining each Major League club, position by position. Each Wednesday until Spring Training camps open, we'll preview a different position. Today: Starting rotation.

ST. LOUIS -- For years the bulwark of the National League Central's dominant franchise, the St. Louis starting rotation now is defined more by who's not available than by who will be taking the ball.

Ace Chris Carpenter is out until at least the All-Star break following reconstructive elbow surgery. Presumptive No. 2 starter Mark Mulder likely won't pitch until May 1 at the earliest, and his most recent shoulder surgery means his effectiveness will be in question when he does return.

It's not the push-button, roll-over-every-five-days squad of the Cards from 2004 and 2005. And it's a big reason why prognosticators are down on St. Louis for 2008. Adam Wainwright heads a rotation that has the possibility of being very good but little certainty.

"Our rotation has a lot of potential," said Wainwright. "You look at the numbers, when Carpenter gets back we could go from having one of the most questionable staffs to one of the best, without a doubt. I think it all depends on how the guys that are coming off of injury can come in and perform."

Wainwright is the ace, at least until the big guys return. He rebounded from a slow start to put up an excellent season, finishing 14-12 with a 3.70 ERA. From May 22 until the end of the season, his ERA was a spiffy 2.96, and he racked up 110 strikeouts against 48 walks.

After that, though, it's a little muddled. Braden Looper and Joel Pineiro seem all but sure things to start from the beginning of the season. Looper contributed 175 innings of more or less average work in his first year as a starter, while Pineiro looked strong in his first season in the National League.

St. Louis Cardinals
• Catchers: Molina continues to improve
• Corner IF: Cards counting on duo
• Middle IF: Izturis ready to step in
• Outfielders: A new look this season
• Starters: Questions surround rotation
• Bullpen: Wainwright ready to fill in
• Bench: Who are the role players?

Matt Clement was signed to be part of the rotation, but given that Clement hasn't started a big league game since 2006, he remains something of a seeing-is-believing proposition. Still, Clement has been excellent in the NL Central in the past, and hopes are high.

Then there's the five spot. Anthony Reyes is the favorite to hold down that job until Mulder returns, but he is far from a guarantee. He'll likely get competition from Todd Wellemeyer and perhaps Brad Thompson. It's not inconceivable, but it is quite unlikely, that a prospect from the Minor Leagues could make a push, such as Jaime Garcia or Mitchell Boggs.

Whoever constitutes the five at the start of the season, the cast has a chance to be good. But it's unlikely the Cardinals rotation will be great until and unless the two ailing aces return to form.

"You hope for the best, prepare for the worst," said manager Tony La Russa. "I believe that we will get Mark and Chris sometime in the '08 season. In the meantime, they probably won't be there Opening Day. And the games count. So we need to pitch well enough to get off to a good start. When they come, they come. But we'll pitch somebody else until they get there."