McClellan seeks to follow up another strong outing from Kyle Lohse and remain undefeated when the Cardinals conclude their three-game road set against the Houston Astros on Thursday.
Lohse pitched seven scoreless innings Wednesday to improve to 4-1 as the Cardinals (13-11) held off a late Houston rally to even this series with a 6-5 victory.
Now, McClellan (3-0, 2.16 ERA) has the chance to match Lohse's win total as he concludes a stellar first month as a full-time member of the starting rotation.
The right-hander, who has spent his first three seasons pitching out of the St. Louis bullpen, has allowed no more than two runs in any of his four outings. He gave up two runs in six innings of a 4-2 win over Cincinnati on Friday, in what was technically a relief appearance after substitute starter Miguel Batista faced one batter before a lengthy rain delay.
"I'm not a very patient person so it was a little difficult but not too much different than what I've done in the past," McClellan said.
One key reason for McClellan's early success is his skill at getting out of jams. Opposing hitters are 3 for 29 against him with runners in scoring position this season.
McClellan is 0-2 with two saves and a 2.89 ERA in 17 relief appearances against the Astros. This will be his first start versus Houston.
He looks to help the Cardinals win the series after Wednesday's win snapped a four-game road skid to the Astros (9-15). Matt Holliday went 3 for 4 with a homer and two RBIs while Lance Berkman added two hits in his second game against his former club.
Batting .429 on the season, Holliday is 5 for 8 in the series and has four homers with 11 RBIs his last eight games at Minute Maid Park.
Berkman is hitting .385, and is riding a streak of six straight multi-hit games.
Cardinals slugger Albert Pujols went 1 for 4 on Wednesday, one day after a sore hamstring and a cold limited him to a pinch-hitting appearance in Tuesday's 6-5 loss.
Pujols, Berkman and Holliday are a combined 6 for 32 with two homers against scheduled Houston starter Nelson Figueroa (0-3, 8.55).
Figueroa has struggled this season, allowing 19 earned runs and 31 hits in 20 innings over four starts. The right-hander gave up six runs and walked five in four innings of a 14-7 loss at Milwaukee on Friday.
Figueroa is 1-1 with a 5.54 ERA in five starts versus St. Louis. He earned the win by allowing two runs in five innings of a 5-2 home victory Sept. 1.
Brett Wallace had his second straight three-hit game Wednesday for the Astros, who scored five runs in the final two innings but lost for the fourth time in six games.
"They know that it can happen,'' manager Brad Mills said of his team's ability to come back. "We have seen that more than once, especially in the last two weeks."
Wallace is 16 for 29 with five doubles in his last seven games, and 12 for 21 in eight career contests against St. Louis.