Wacha has two victories over his last five outings, including a triumph over the San Francisco Giants on Saturday. Wacha logged six scoreless innings of three-hit ball, striking out seven without issuing a walk.
The 22-year-old righty has yet to allow more than three runs in a start this season and sits at 4-3 with a 2.45 earned run average.
Wacha will face the Royals for the second time in his career tonight and did not get a decision the first time he faced them despite an excellent showing. He allowed just one run on two hits over seven innings, fanning six without a walk.
The Royals will be glad that they can counter with young hurler Yordano Ventura, who gave his club a scare in his last outing back on May 26.
The right-hander lasted just 2 2/3 innings and gave up five runs in a loss to Houston, exiting with elbow discomfort.
"In the third inning, I threw a few pitches and it started to feel a little weird," Ventura said of the elbow. "I felt something unnatural. It was a little uncomfortable, unnatural, and I decided to say something."
Ventura, who turned 23 this past Tuesday, had his last start skipped, but has made it through all of his side sessions without issue.
The talented arm hasn't won since April 25 and has lost four straight starts, falling to 2-5 on the year with a 3.45 ERA. That includes an 0-4 mark with a 4.50 ERA in six games at home and he'll try to find the win column tonight in his first meeting with the Cardinals.
St. Louis lost the first two games of this series at home, but battled back last night in Kansas City for a 5-2 victory in 11 innings.
Cards ace Adam Wainwright took a shutout into the ninth inning, but the first batter he faced in the frame reached base on a dropped third strike. Billy Butler then singled to chase Wainwright and closer Trevor Rosenthal walked Alex Gordon to load the bases.
A fielder's choice grounder by Salvador Perez scored a run and Lorenzo Cain tied the contest with an RBI single.
"Even going into the ninth inning with two or three hits, whatever we had, we still felt as a group we had a chance to win the ballgame and that's a good feeling," Royals manager Ned Yost said.
It was not to be as Matt Carpenter's fifth hit of the game, a double in the 11th inning, scored a run and Allen Craig later smacked a two-run single in the frame as the Cardinals snapped a three-game slide with just their second victory in eight games.
"Tonight, that's one of those special nights where things are just falling into place," said Carpenter, who reached base six times in all. "I'm seeing the ball well and putting good swings on it."
Despite taking the first two contests of this four-game home-and-home set, the Royals have only beaten the Cardinals six times in the last 18 encounters following last night's defeat. St. Louis won three of four in the series a season ago.