Sidelined since May because of a knee injury, St. Louis' Lance Berkman comes off the disabled list in Cincinnati - one of his favorite places to hit.
Potentially making matters worse for the Reds is Cardinals scheduled starter Kyle Lohse has routinely shut them down.
St Louis tries to bounce back from a disappointing loss behind Lohse and Berkman on Saturday and prevent Cincinnati from a fifth straight win.
The Cardinals (46-41) led Friday's series opener 2-1 in the seventh inning until first baseman Allen Craig's throwing error allowed two runs to score, paving the way for the Reds to win 5-3. Brandon Phillips had three hits and scored twice for Cincinnati (48-38), which moved into a first-place tie atop the NL Central with Pittsburgh.
"People are excited," Dusty Baker said. "I hope they stay that way until the end.''
The Cardinals, 2 1/2 games out of first, have reason to be excited Saturday.
Berkman is returning ahead of schedule after undergoing surgery to repair torn cartilage in his right knee, which was sustained while stretching for a throw on May 19. He didn't want to go on a minor league rehabilitation assignment, preferring to ease back into an everyday role in the majors by sharing time at first with Craig and Matt Carpenter.
"There's really not a whole lot you can fine-tune until you get back in there and start playing against live competition,'' said Berkman, who hit .333 in 13 games before his injury. "For me, it's just making sure I get my body in shape to swing the bat. I don't expect to step back in there and be in midseason form.''
The veteran slugger could be used as a pinch hitter because he's not in the starting lineup, and that may be good news for the Reds.
He is 5 for 13 against Cincinnati this season and his 23 homers at Great American Ball Park are the most by any visiting player. Maybe one reason he's not starting is that he hasn't had much success against probable starter Mike Leake (3-6, 4.01 ERA), going 1 for 11.
Lohse (9-2, 2.79), meanwhile, has a 1.59 ERA in his last six starts against the Reds, surrendering two runs or less in each.
Lohse has also permitted two runs in winning each of his last three starts, and has a 2.01 ERA in his last seven.
"I think I've really figured out what it takes to be successful and that's going out and locating, not trying to overpower anybody, using my defense,'' Lohse said after allowing three hits and a walk over seven innings in a 3-2 win over Miami last Saturday.
Leake has been enjoying similar success lately.
He had a 1.74 ERA in his final four starts before the break, shaving more than a run off his ERA from 5.05. In his last start against the Los Angeles Dodgers on July 4, he allowed three runs - all in the first - and six hits over seven innings of a 4-1 defeat.
This will be the right-hander's first start against the Cardinals since yielding three runs in six innings of a 3-1 loss in his season debut on April 10.
Lohse got the victory in that game, allowing a run and four hits in six innings. He made his next start against the Reds on April 17, and gave up four hits in seven shutout innings.
Joey Votto is 2 for 5 against Lohse this season, and fellow All-Star Jay Bruce is 2 for 6.
Matt Holliday, batting .400 with 10 RBIs during a 12-game hitting streak, is 4 for 8 lifetime against Leake.