One of those things will happen Saturday at Wrigley Field, where the struggling Cardinals look to spoil Cubs starter Jake Arrieta's season debut.
Wacha (2-2, 2.48 ERA) has pitched well with a 1.53 ERA in three road starts but has lost both decisions, receiving two runs of total support in those outings.
St. Louis (15-15) surprisingly has one of baseball's worst offenses, averaging 3.7 runs. The Cardinals averaged an NL-best 4.8 a year ago.
Chicago (10-17) has been better with 3.9 runs per game but is the only team in the majors yet to claim a series victory. The Cubs are in search of their first three-game win streak since July 26-28 after holding on for a 6-5 victory Friday to open this three-game set.
Wacha presents a formidable opponent with a strikeout per batter faced ratio of .289 that is one of the majors' best. The right-hander has struck out 19 in his last two outings, registering nine over 6 1-3 innings Monday as he allowed three runs in a 5-3, 12-inning loss to Milwaukee.
''I felt good with all of my pitches and command,'' Wacha said.
Wacha's last win came against Chicago on April 13, allowing three runs and striking out eight in 6 1-3 innings of a 6-4 victory.
The Cubs are anticipating a boost from Arrieta, who will be activated off the disabled list after being out due to shoulder tightness.
The right-hander went 4-2 with a 3.66 ERA in nine starts last year for Chicago, which acquired him from Baltimore on July 2. He made five rehab starts in the minors and was originally set to return Wednesday before rain forced the Cubs to shuffle their rotation.
"I know what I'm capable of," he told the Cubs' official website. "The work that I put in - I think the sky's the limit. I think I can be a guy that this team can rely on for a long time. I showed a lot of that last year and I'm confident that I could pick up where I left off and be even better than that. I'm very confident."
Arrieta was brilliant in his lone start against the Cardinals, yielding two hits in seven innings with seven strikeouts in a 7-0 home win Aug. 16.
Anthony Rizzo homered for the second game in a row Friday, also going deep for the second straight time he has faced St. Louis. Rizzo homered last month off Wacha.
''I'm not trying to do too much,'' said Rizzo, who has five of his 15 RBIs in the past two games. ''See the ball and hit it, really try to swing at the pitches I want to hit, not pitcher's pitches."
Cubs center fielder Ryan Sweeney was removed Friday after injuring his right hamstring on a running catch in the eighth inning. He went 2 for 3 with an RBI after going hitless in eight at-bats over his previous three games.
St. Louis catcher Yadier Molina is 19 for 37 over a nine-game hitting streak against Chicago.