Overbay was walking around the visitors' clubhouse on Wednesday with a large bandage covering his stitches.
Overbay was named the Brewers' Most Valuable Player in 2004 after batting .301 with a National League-high 53 doubles. He hit .370 with four doubles, two home runs and 10 RBIs in 25 spring games, and is hitting .277 with two home runs and nine RBIs so far this season.
The left-handed hitting first baseman took a six-game hitting streak into Tuesday's game. Overbay was batting .348 (8-for-23) during that stretch and had settled comfortably into the No. 5 spot in the lineup after hitting in the No. 3 hole for 15 games this season.
"You just hate to see that happen," Yost said of Overbay's injury. "He's such a big part of our offense and our team and he's such a great kid. I'm just glad it's a minor thing."
Lineup changes: Yost had to shake up the lineup a little bit with Overbay unable to make Wednesday's start.
Jeff Cirillo, who replaced Overbay on Tuesday and reached base in three of his four plate appearances, made his ninth start at third base and started in the No. 2 spot in the lineup for the first time this season.
"That's the kind of player he is," Yost said. "That's why we like him on the team. He gives you a great quality at-bat just about every time and he plays solid defense."
Cirillo entered Wednesday's game hitting .229 with one home run and six RBIs. He is batting .352 (60-for-170) against the Cardinals during his career, with six home runs and 32 RBIs.
Russell Branyan, who has started nine games at third base, moved over to first base and into the No. 5 spot in the batting order. He entered Wednesday's game hitting .314 with three home runs and nine RBIs.
Praise for Santos: Yost had nothing but positive things to say about Wednesday's starter, right-hander Victor Santos, a couple hours before the game.
"He's coming off a good winter where he didn't go play winter ball," Yost said. "He's come on real strong and he's really throwing the ball very well for us. He's throwing strikes. He's got good command on four pitches, really -- fastball, a bit of a slider-curveball and a nasty split. He's throwing a good changeup. He's been our best pitcher so far this year to date."
Santos entered Wednesday's contest with a 1-0 record and a 1.64 ERA. He ranked second in the National League with a .158 opponents' average and eighth in the league in ERA.
Lee struggling vs. Cards: Left fielder Carlos Lee's struggles against St. Louis continued on Tuesday night. Lee, who hit two home runs in Sunday's win at San Francisco, went 0-for-4 with a pair of strikeouts on Tuesday and is now hitless in 16 at-bats against the Cardinals this season.
"It's just a case of him getting back into his game plan and not swinging at those balls off the plate," Yost said.
Lee entered Wednesday's game batting .247 with three home runs and 14 RBIs.
On the farm: The Double-A Huntsville Stars lost for the ninth time in 12 road games this season and fell to 9-10 overall in losing to the Mississippi Braves, 5-0, in Pearl, Miss.
Outfielder Tony Gwynn Jr. had a single and a double and was the only Huntsville batter to reach third base. He extended his hitting streak to five games.
The Stars will finish up their three-game series with the Braves Wednesday night, and will begin a four-game series with the Tennessee Smokies at home on Thursday night.
On deck: The Brewers and Cardinals will make up Monday's rainout with a 1:10 p.m. CT start on Thursday at Busch Stadium. Left-hander Chris Capuano will make the start for Milwaukee against St. Louis right-hander Jason Marquis.