CHICAGO — Hitters are adjusting to Jake Arrieta. Now the Chicago Cubs ace has to counter.

Arrieta labored through five innings, Michael Wacha pitched into the seventh for his first win in nearly two months and the St. Louis Cardinals roughed up Chicago’s bullpen in a 7-2 victory Wednesday.

Aledmys Diaz hit a two-run home run, and Matt Carpenter had a two-run double in a five-run sixth after Arrieta (11-2) departed.

“It’s adjusting the game plan slightly,” Arrieta said. “Just going a different route and being aggressive early and putting the hitter in a hole versus being in 1-0, 2-0 counts. That’s what they want. They’re taking the first pitch hoping I’m outside the strike zone.

“I’ll adjust accordingly.”

The Cardinals won their eighth straight road game — their longest streak since 1982 — and completed their first three-game sweep at Wrigley Field since 1988. They had a patient approach, drawing four walks off Arrieta and making the reigning NL Cy Young Award winner throw 106 pitches.

“We grinded one through nine,” Carpenter said. “Even Wacha had a pretty long at-bat (seven pitches) against him. We worked his pitch count and had runners on base.”

The fifth inning was a prime example. A single and two walks loaded the bases with one out when Stephen Piscotty hit a grounder to third. Chicago second baseman Ben Zobrist’s relay throw to first was a one-hopper and first baseman Anthony Rizzo couldn’t dig it out for the double play, and two runs scored on the error.

“Jake struggled through the five but could have got out of it with nothing and we could have moved it along in a different way,” Cubs manager Joe Maddon said. “But that play really gave them some momentum and their guy pitched well.”

Wacha (3-7) allowed two hits until rookie Willson Contreras’ one-out, two-run homer in the seventh ended his day. He snapped a seven-game skid.

Contreras replaced Miguel Montero an inning earlier after the catcher twisted his right knee. The Cubs had three hits and several mental and defensive miscues.

Chicago entered the series with a 12½-game lead over second-place St. Louis in the NL Central.