Heading into Monday's series opener of a three-game set at Busch Stadium, the Cardinals are in second place in the National League Central and the Reds are fourth, both chasing the first-place Brewers. St. Louis has won all three of its series against the Reds this year, going 6-3 overall. The teams haven't met since May.
The Cardinals will start the series with Justin Masterson on the mound, coming off his third and best start for his new team. The right-hander, acquired in a trade from Cleveland, threw seven scoreless innings in Miami on Wednesday, allowing only three hits after implementing some of the mechanical adjustments that the team's staff suggested. He'll throw to A.J. Pierzynski for a second straight start since their last collaboration was so successful.
It was the first time since June 19 that Masterson pitched more than six innings, and Cardinals manager Mike Matheny said he was trending in the right direction.
"Even in the seventh when he started to look like he might have lost his rhythm, he gathered it back together," Matheny said. "That leads us to believe that [his performance is] something that's repeatable."
The Reds will start Mike Leake, who had given up only three earned runs over his previous 20 2/3 innings before he gave up five in five innings in his most recent outing. He tripped up early in a two-run first and allowed the Red Sox to tack on three in the fifth.
"Any time you score runs and go right back to giving them up the next inning is not ideal, especially when you give up a three-run inning," Leake said afterward.
The Reds will certainly be looking for him to do better Monday night as they try to get back into the thick of the divisional race.
Reds: Frazier fighting an aching back
Todd Frazier missed Sunday's doubleheader at Coors Field with a lingering sore back.
The back problems started Thursday when he was injured swinging the bat against the Rockies' Jorge De La Rosa. Frazier did not play Friday and was not in Saturday's lineup before the game was postponed.
"Usually when I have this, it takes a couple of days. But it's nagging right now. We'll see how it goes," he said.
Frazier leads Cincinnati in batting average, home runs, RBI and on-base percentage.
Cardinals: Holliday expected back in lineup
After sitting out Sunday's game against San Diego, Matt Holliday is expected back in the lineup for the series opener with the Reds.
The outfielder has been struggling lately, entering Monday on an 0-for-19 skid and dealing with some discomfort in his left knee. Holliday has started 119 of the team's 123 games this season.
"I think they're interrelated," Matheny said of Holliday's knee troubles and results. "He's trying to grind for us because we need everyone to grind for us right now. He's feeling it. You can tell by some of his movements."
• Masterson is on a three-game win streak against Cincinnati.
• The Cardinals have won 10 of their last 11 series against the Reds.
Caitlin Swieca is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.