PHOENIX — The St. Louis Cardinals made moves this morning to protect a spent bullpen and will make a move Friday to address the opening in their starting rotation. Righthander P.J. Walters is scheduled to make his major-league debut, starting Friday against the Chicago Cubs at Wrigley Field.

Manager Tony La Russa said the other starters will shift back a day for a couple reasons: First, to keep Walters on his normal schedule; he was set to pitch Friday for Class AAA Memphis. And, second, to avoid having the rookie make his major-league debut on national television Sunday night at Wrigley.

The rotation for the coming series against the Cubs then is:

• Thursday, Adam Wainwright
• Friday, P.J. Walters
• Saturday, Kyle Lohse (on an extra day’s rest)
• Sunday, Todd Wellemeyer (on an extra day’s rest)

Chris Carpenter, who went on the disabled list morning, was scheduled to make the start Sunday. La Russa said Walters will get first crack at the opening in the rotation, and that the fill for that spot is likely to come from within the system as opposed to pulling someone from the major-league bullpen, like Kyle McClellan.

“What you do is (Walters) gets the first opportunity Friday,” La Russa said. “We’ll see how it goes. … It’s a heck of an assignment. He’s a composure guy. He’s used to having a big load on the game.”

Walters was impressive in his first start for Memphis. He pitched seven shutout innings and struck out six against two walks. The righthander has a plus changeup that, early in his professional career, was actually described by scouts as a “screwball.” Walters rejects that description, and he has more velocity on his fastball that expected from a starter who steadily climbed the system with his changeup.

Walters was drafted 346th overall in the 2006 draft.

The Cardinals will have to make a move Friday morning to make room on the roster for Walters. La Russa said that move is likely to be a pitcher optioned out to Memphis, though the next two games could play a role in dictating who it will be.

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