CHICAGO -- Curtain calls are becoming a trend for the Chicago Cubs.

On Sunday night, it was rookie Ian Happ's turn to climb the dugout steps and salute a sellout crowd. The 22-year-old smiled and waved after belting his second home run of the game.

The Cubs held on for a 7-6 win to complete a three-game sweep over the St. Louis Cardinals.

"Awesome moment," Happ said. "These fans are unbelievable."

Happ notched his first career multi-home run game and drove in a career-high four runs to lead the Cubs. Pinch-hitter Jon Jay drove in the go-ahead run in the seventh inning

Chicago (28-27) improved to 17-11 at Wrigley Field and climbed above .500 for the first time since May 28. The Cubs completed their first three-game sweep over the Cardinals since Sept. 13-15, 2010.

Stephen Piscotty hit a three-run home run to lead the Cardinals at the plate but committed a costly error in right field. Aledmys Diaz added a pair of doubles and an RBI in a losing effort.

St. Louis (26-28) suffered its eighth loss in the past 11 games.

"When things started to go bad, they went bad in a hurry," Cardinals manager Mike Matheny said.

Cubs right-hander Pedro Strop (2-2) pitched 1 2/3 scoreless innings of relief to earn the victory. Strop was one of five relievers to bail out starter Kyle Hendricks, who gave up four runs in four innings.

Cardinals right-hander Matt Bowman (1-2) drew the loss out of the bullpen.

Jay broke a 6-6 tie with a line drive to left-center field that scored Anthony Rizzo from second base. The former Cardinal has gone 9-for-20 (.450) with three RBIs as a pinch hitter this season.

"Jon Jay is such a valuable baseball player," Cubs manager Joe Maddon said. "I was thinking about it, it's kind of like John Havlicek. The sixth man in basketball becomes famous.

"He's the sixth man here. You can pop him in there, and it's like instant offense. You know something good possibly can happen. You know he's ready."

Jay's hit spoiled a comeback bid for St. Louis, which scored twice in the sixth to even the score. Paul DeJong and Diaz each drove in a run during the frame.

Right-hander Koji Uehara picked up his second save with a scoreless ninth.

Chicago opened the scoring on a solo home run by Happ in the third. The rookie hooked a towering fly ball just inside the right-field foul pole.

The Cardinals turned to the long ball to pull ahead in the fourth. After Dexter Fowler and Matt Carpenter drew a pair of walks, Piscotty launched a three-run home run into the left-field bleachers.

DeJong drove in Jedd Gyorko with a single later in the inning to increase St. Louis' lead to 4-1.

The lead vanished in a hurry as the Cubs scored five runs in the fourth to regain a 6-4 advantage. Miguel Montero and Addison Russell started the comeback when they scored on a pinch-hit single by Albert Almora that rolled underneath Piscotty's glove for a two-base error.

Two batters later, Happ pulled a three-run blast into the right-field bleachers for his second home run of the game and his fourth of the season.

"That ball was really properly struck," Maddon said. "That had that second gear on it."

Cardinals right-hander Michael Wacha blamed himself for allowing the Cubs back in the game. Wacha gave up six runs on six hits in 4 1/3 innings but received a no-decision.

"That's on me," Wacha said. "Guys have been giving me a lead out there, and I've just been serving it right back to them. That's not the way to go about it.

"Whenever we get a lead, that starter is supposed to go out there and keep that lead for us, and I haven't been doing that."

NOTES: The Cubs held a moment of silence before the game to honor former big league player, coach and broadcaster Jimmy Piersall, who died Saturday at age 87. ... Cardinals 3B Jedd Gyorko was activated from the paternity list and went 1-for-4. Gyorko and his wife, Karley, welcomed a daughter, Brooklyn Ellee, on Tuesday. The couple also has 3-year-old twin boys. ... Cubs SS Addison Russell returned to the starting lineup and 2B/SS Javier Baez came in off the bench as manager Joe Maddon continues to rotate playing time for the duo. ... The Cardinals optioned OF Magneuris Sierra to Double-A Springfield. Sierra has hit safely in all eight games he has played in the majors. ... Cardinals 2B Kolten Wong is slated to begin a minor league injury rehabilitation assignment this week. He has been on the disabled list since May 27 with a left elbow strain.