CHICAGO (AP) Although Gregory Polanco hasn't always lived up to his advance billing, he showed Saturday night why there was so much hype when he was promoted to the major leagues three years ago.

Polanco hit a two-run homer in the sixth inning and Ivan Nova pitched three-hit ball into the seventh, leading the Pittsburgh Pirates to a 4-2 victory over the Chicago Cubs.

''Gregory's been swinging the bat better,'' Pirates manager Clint Hurdle said. ''The ball's coming off his bat, the velocity, he's covering pitches.''

At 6-foot-5, Polanco can have a long, looping swing, but has been working on being more direct to the pitch and now has an eight-game hitting streak.

''I've been just trying to stay short,'' he said.

Josh Bell had three hits and two runs scored, while Francisco Cervelli and Jordy Mercer each drove in a run for the Pirates.

Ian Happ and Kyle Schwarber had back-to-back home runs for Chicago, which has not won consecutive games since a three-game streak June 18-20.

Nova (9-6) struck out six and walked one in 6 2/3 innings. Besides the homers, the only other hit he allowed was a second-inning single to Schwarber.

''It's what we've seen from this guy since we got him,'' Hurdle said of Nova. ''It was a good mix of pitches.''

Felipe Rivero, who reached 102 on the radar gun, got the final four outs for his sixth save.

Cubs starter Jake Arrieta (8-7) allowed four runs (three earned) and six hits in 5 2/3 innings. He had allowed an unearned run through five innings before being knocked out in the sixth.

''It's my job to hold the lead,'' Arrieta said. ''It's upsetting that I couldn't do that in that situation.''

The Pirates took a 1-0 lead in the fourth. Bell led off with a double, advanced to third on a passed ball and scored on a groundout by Cervelli.

Nova retired 11 of the first 12 batters he faced before giving up back-to-back bombs with two outs in the fourth. Happ hit a 3-1 pitch into the left-field bleachers, while Schwarber's high drive landed about six rows deep into the bleachers in left-center.

Arrieta worked a 1-2-3 fifth after getting the lead, but ran into trouble in the sixth. Bell led off - again - with a double and one out later Polanco homered to put Pittsburgh back on top 3-2. Perhaps most impressive was the homer came on a 92-mph fastball that appeared 6 inches outside.

''It happened so quickly,'' Chicago manager Joe Maddon said. ''Jake was going along very nicely. Historically, Polanco has got not really great numbers against Jake. So, all good - and then a homer.

''That pitch almost looked like a pitchout, it was so far away from him, and he hit it well.''

Cervelli followed with a single and scored all the way from first on a double by Mercer to make it 4-2.

FLIPPING THE SCRIPT

Arrieta has a 7.29 ERA in his last six starts against the Pirates, allowing at least one homer in each outing. Before that, he had a 1.46 ERA in his first 12 starts against the Pirates - including a shutout in the 2015 NL Wild Card game.

BEST AGAINST BEST

With righty Kris Bryant coming to the plate with two outs and one on in the eighth, Hurdle called for left-handed closer Rivero even though right-hander Juan Nicasio was in the game.

''That's the MVP from last year and he's our closer,'' Hurdle said.

Rivero walked Bryant but got lefty Anthony Rizzo to ground out to end the threat.

ROSTER MOVES

The Pirates recalled INF Phil Gosselin from Triple-A Indianapolis and LHP Antonio Bastardo was designated for assignment. Gosselin, 28, batted .135 in 24 games (37 at-bats) during a stint with Pittsburgh earlier in the season.

TRAINER'S ROOM

Cubs: RHP Kyle Hendricks, on the DL since June 5 with right hand tendinitis, will make a rehab start on Monday for Double-A Tennessee.

UP NEXT

Pirates RHP Jameson Taillon (5-2, 2.73 ERA) takes a scoreless streak of 15 1/3 innings into his start Sunday in the finale of the three-game series. Cubs LHP Jon Lester (5-5, 3.94 ERA) looks to bounce back after allowing a season-high six runs in his last start.

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