McClain is the first pitcher in Missouri baseball history to win the award in back-to-back weeks.
The Tigers offense managed to produce eight hits against the Boilermakers but were only able to score in the third inning, when sophomore shortstop Ryan Howard drove in sophomore left fielder Jake Ring for an RBI.
Helping the Tigers improve to 6-1, freshman Tanner Houck allowed just one run.
The Tigers improved to 5-1 after beating Sam Houston State on Friday.
The Tigers lost to the Texas A&M-Corpus Christi Islanders on Thursday night but will have another shot at beating the team Saturday.
In his Missouri debut, McClain threw 10 strikeouts over eight innings in the team's 1-0 victory against Iona last Friday, earning him SEC Pitcher of the Week honors.
McClain threw 10 strikeouts over eight innings in a 1-0 victory over Iona on Friday.
Junior pitcher Alec Rash struggled with control, walking four, but struck out five in 4.1 innings of one-run ball during Missouri's 14-2 victory over Iona Saturday.
Freshman pitcher Tanner Houck earned a win in his debut.
John Dettmer, who was inducted into the Missouri Intercollegiate Athletics Hall of Fame Friday, holds the Missouri baseball record for career strikeouts with 374, but unlike other inductees no longer plays sports.
The Tigers only run came in the fifth inning when freshman catcher Brett Bond drove in freshman designated hitter Trey Harris with an RBI single.
The Tigers overcame a 3-0 deficit in the final three innings, ending a nine-game losing streak that started last season.
The NCAA and the Missouri Tigers are counting on a small change in stitching on the baseball to make a big difference in performance on the field.
Missouri baseball Tigers to play two games on Friday.
Missouri baseball has four freshman pitchers all 6-foot-5 or taller.
The Tigers start their season with two road trips against four unranked teams.
The Tigers will play nine games broadcast on the SEC Network in 2015.
When Charlie James played in the outfield for the Missouri baseball team, his powerful throwing arm caught the eye of talent scouts for the St. Louis Cardinals, who signed him to a $15,000 contract in January 1958.
The Tigers start their season on Feb. 13 against Iona.
The rule changes varied from allowing of umpires to conference over a catch in the outfield to requiring all schools to paint their foul poles fluorescent yellow.