HOUSTON -- In a show of optimism regarding Chris Duncan's left knee, the Cardinals elected not to place Duncan on the disabled list on Saturday. Instead, they optioned left-hander Troy Cate to Triple-A Memphis in order to make room for Brendan Ryan, who was called up from Memphis.

Ryan was needed because injuries to infielders Scott Rolen and David Eckstein left the Cardinals without a healthy extra infielder. Scott Spiezio started at third base and Aaron Miles at short, with no one but Ryan available to back them up if something were to happen to Spiezio, Miles or second baseman Adam Kennedy.

As of Friday night, the Cardinals had expected to place Duncan on the disabled list with an infection in his left knee in order to make room for Ryan. But medical reports indicated continued progress for Duncan, so the decision was made to send Cate out instead.

"He made improvement," said manager Tony La Russa. "We don't want to bang him until it's really necessary, and there's a different way to go."

Duncan could be available as soon as Tuesday. He is expected to work out and take some batting practice on Sunday.

Ryan, 25, was batting .243 with a .303 on-base percentage and a .318 slugging percentage at Memphis. He has played exclusively at shortstop for the vast majority of his professional career, but he's gotten some work at second and third base in Spring Training. He was informed that he'd gotten "the call" following Memphis' game on Friday.

"After the game, Anthony [Reyes] bought the spread and I was hanging out enjoying a nice meal," Ryan said. "Hammer [manager Chris Maloney] called me in and was like, 'I've got some bad news for you. We're not going to have you around here anymore.'"

Ryan made his way to Houston, and was dressed and ready to go for Saturday's game.

Rolen, Eckstein sit: Rolen and Eckstein were both held out of Saturday's lineup, but both professed optimism about their injury prognoses. Eckstein said he wouldn't rule out a return to the lineup on Sunday, while Rolen could play again on Tuesday following an off day Monday.

"I think there's a chance," Eckstein said when asked about his availability in this weekend's series.

Eckstein all but ruled out the possibility of wearing an elbow pad to protect his left elbow, which was hit by a Roy Oswalt pitch on Friday night.

Rolen said that he is much improved from Friday, when he was sore before the game and didn't improve as he played.

"He's sore and it's hard to visualize having him over the weekend," La Russa said. "Hopefully it's one of those minor things that clears up quickly. He's been playing like he can play, so we definitely don't want to lose him."

Déjà vu for Reyes: Reyes had an unpleasantly familiar experience in his first game since being optioned to Memphis. Reyes pitched an outstanding game, allowing a run on three hits over seven innings, but left the game trailing, 1-0. He struck out four, didn't issue a walk and threw 71 strikes among his 98 pitches.

This date in Cardinals history: On June 2, 1967, Lou Brock hit a two-run homer and Steve Carlton pitched a complete game as the Cardinals beat the Cubs, 2-1, at Busch Stadium. Carlton allowed three hits and struck out six in a game that lasted only an hour and 45 minutes. Thanks to Project Retrosheet for the information.

Baby 'Birds: Memphis' bullpen unraveled in a six-run ninth inning, and the club lost to Tucson, 7-1, on Friday. John Rodriguez homered. ... Double-A Springfield and Class A Palm Beach were both rained out. ... Tyler Herron dominated for five innings and Christian Reyes hit his third home run in two days as Class A Quad Cities beat Clinton, 10-5. Brandon Buckman added two hits, two walks and three runs. Herron struck out eight against one walk, allowing a run on two hits. In his last six outings, the righty has a 1.98 ERA in 27 1/3 innings with 29 Ks and six walks.

Christian Reyes is the player of the day as he keeps raking in his first taste of full-season ball. Reyes, 21, is batting .347 with a .587 slugging percentage in 21 games, playing catcher and designated hitter. He was the Cardinals' 27th-round pick in 2006 out of a California junior college, and split his first pro season between rookie-level Johnson City and short-season State College.

Coming up: The Cardinals wrap up their seven-game road trip with a Sunday afternoon game at Minute Maid Park. Braden Looper will try again for win No. 7 when he goes up against Jason Jennings. First pitch is set for 1:05 p.m. CT.