– Matt Szczur merely needed a fly to win the game. He just didn’t think — and neither did anyone else at Wrigley Field — that the ball he hit would do the trick.

That is, until Pittsburgh right fielder Gregory Polanco took a most startling trip.

Polanco slipped and fell while trying to catch an easy fly, and the ball dropped for an RBI single in the 12th inning that sent the Chicago Cubs over the Pirates 11-10.

“That’s not how we drew it up,” a stunned Szczur said. “That’s for sure.”

The Cubs won their fifth straight game in unlikely fashion, and matched their longest string since last June.

Chicago loaded the bases with one out in the 12th against Radhames Liz (0-1), and the Pirates went to a five-man infield. Szczur lifted a routine fly to shallow right, surely not deep enough to score the winning run.

Polanco came running in with plenty of time to make the grab, then stumbled to the ground. He reached up with his bare left hand trying to make a play, but had no chance.

Sprawled in the grass, his sunglasses flying off his head, Polanco never came close to touching the ball as Starlin Castro ran home.

“He didn’t have to go far to get the ball and then he made a little move to his left and crossed his feet,” Pirates manager Clint Hurdle said. “That just took him out of the play, took him down to the ground.”

Polanco wasn’t at his locker in the aftermath of the loss.

Rookie Kris Bryant hit his fourth homer and drove in four.

The Pirates scored four times in the eighth on a solo homer by Josh Harrison and a three-run shot from Andrew McCutchen.