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

ST. LOUIS -- Cardinals fans have gotten used to turnover on the right side of second base. Change on the left side, though, that's a little harder to swallow.

Over the past 30 seasons, five men have served as St. Louis' primary shortstop -- Garry Templeton, Ozzie Smith, Royce Clayton, Edgar Renteria and David Eckstein. Every one of them made an All-Star team while playing for the Redbirds. Occasionally, due to injury or a late-season trade, someone else has held down the position for a month or two, but that list is close to exhaustive.

Into that line steps Cesar Izturis, inked to a one-year deal and possibly only a bridge to the future. Izturis signed early in the winter, bringing a prominent defensive reputation and a bat that hasn't produced much for most of his career. Still, if Izturis can be the kind of defender he was with the Dodgers -- before he needed major elbow surgery -- he brings a fielding upgrade at the most important position in the infield.

At the keystone, however, is where the Cards have the greatest uncertainty on their roster. Adam Kennedy signed a three-year deal before the 2007 season, then promptly endured the toughest season of his big league career. Knee surgery ended Kennedy's season after 87 games, but it likely would have been a lost season if he'd played 140.

The Cardinals, however, are optimistic Kennedy can regain the level of aptitude he showed for seven years in Anaheim -- not a starring role, but a dependably able ballplayer.

"Obviously he has a lot to prove this year," said general manager John Mozeliak. "He has to go out and show up in shape and show that he's ready to contribute. I think he got off to a slow start last year and never really got on track. I know he's been working very hard this offseason to right his ship, and I'm excited to see it."

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?

Mozeliak does not believe Kennedy was playing with an injury in the first half of the season, however.

"His preparation going into the season leads me to be encouraged," Mozeliak said. "But I don't think there's anything you can point back to that says physically he was impeded."

The primary backup is Aaron Miles, re-signed for one more year after being non-tendered. Miles' return may force out youngster Brendan Ryan, who impressed as a rookie in 2007 but has no guaranteed spot on the '08 Cards.

The Cardinals signed D'Angelo Jimenez to a Minor League deal with an invitation to big league Spring Training, but like Ryan, Jimenez may face a numbers crunch.

Second baseman Jarrett Hoffpauir, who had a breakout year in 2007, and third baseman/shortstop Brian Barden, likely are ticketed for Triple-A Memphis.