Matheny left his ace in for one more hitter with two on and Wainwright responded with one more big pitch, and then left the mound with a whoop in a 5-2 victory over the Boston Red Sox on Thursday night.
"That was a couple weeks of frustration built up, just not making a pitch when I needed to," Wainwright said. "He just came out and gave me a little pep talk.
"He's a motivational speaker guy, he's very good at that."
"He's one of the top pitchers and when they get into trouble they find ways to get out of it," Boston second baseman Dustin Pedroia said. "That's what he did. That's why he's one of the best."
Wainwright recovered from a shaky start to earn his 14th win, tying for the major league lead, and rookie Kolten Wong homered twice.
"He's got really impressive bat speed, always has," Matheny said of Wong. "You don't have to cheat. You just take the head of the bat to the ball and watch it jump."
Jhonny Peralta's two-run double keyed a three-run first off Brandon Workman and Wong had his first multihomer game. The Cardinals took two of three from their stripped-down opponents, who beat them in the World Series last fall but are in last place in the AL East.
"That first inning is kind of notorious in his career," Red Sox manager John Farrell said of Workman.
Wainwright (14-6) needed 66 pitches to slog through the first three innings after the start was delayed by rain for more than an hour for the second straight night. The 6-foot-7 right-hander retired 11 in a row before the seventh.
Wainwright has won at least 14 games each of the last three seasons. Wily Peralta won his 14th game earlier Thursday for the NL Central-leading Brewers, who are one game ahead of St. Louis.
Workman (1-5) retired nine straight before Wong lined a 1-0 pitch over the right-field wall with one out in the fifth to put the Cardinals up 4-2. Wong then added his ninth homer in the seventh, a 423-foot shot off Craig Breslow.
Mike Napoli and Christian Vasquez each drove in a run in the third, Wainwright's roughest inning. He had seven strikeouts and allowed seven hits, four of them in the third.
Workman has totaled 70 pitches in the first inning his last two starts, allowing five runs. He faced eight batters in St. Louis' three-run first.
Red Sox: David Ortiz was scratched because of concerns with wet grounds and Napoli got the start at first base instead. Ortiz pinch-hit in the eighth and lined out. Allen Craig (left foot sprain) is visiting with specialist Dr. Robert Anderson in Charlotte, N.C., on Friday and will rejoin the team in Los Angeles.
Cardinals: Closer Trevor Rosenthal made his fourth straight appearance in a five-day span on Wednesday and took the loss, surrendering the go-ahead run. He didn't warm up during the finale. All-Star setup man Pat Neshek finished for his third save in five chances, and first since June 17. "(Rosenthal) could have said whatever he wanted to say, it didn't really matter tonight," Matheny said.
The Cardinals sent Justin Masterson (1-0, 7.50 ERA) ahead to Baltimore, where he will oppose Chris Tillman (8-5, 3.78 ERA) on Friday night. He is 2/3 with a 6.98 ERA in six starts at Camden Yards. The Red Sox begin a three-game series at Los Angeles, with Allen Webster (1-1, 6.75 ERA) opposing the Angels' Jered Weaver (12-6, 3.59 ERA).
The Cardinals have won all four interleague series against the Red Sox and are 8-4 overall. ... Boston center fielder Jackie Bradley Jr. was hitless in three at-bats before coming out in a double switch and is in an 0-for-27 slump.