PITTSBURGH (AP) Pinch-hitter Josh Harrison singled home Francisco Cervelli with the go-ahead run in the eighth inning and the Pittsburgh bullpen continued its hot streak in the Pirates' 5-3 victory over the Colorado Rockies on Friday night.

Gregory Polanco had three hits, drove in an insurance run and preserved a tie by throwing out Jose Reyes of the Rockies at the plate from right field to end the top of the eighth.

Tony Watson (3-1) earned the win with a scoreless inning of relief. Mark Melancon worked a perfect ninth for his major league-leading 42nd save. Pittsburgh relievers have won 18 straight decisions since last taking a loss on June 25.

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The Pirates improved to 13-3 over their last 16 games to strengthen their grip on the top wild card spot in the National League.

Reyes hit his third home run of the season for Colorado. Carlos Gonzalez added his 31st but the Rockies dropped their sixth straight game to the Pirates. Scott Oberg (3-3) issued consecutive walks to Cervelli and Pedro Alvarez in the eighth to set up Harrison.

Colorado rookie starter Jon Gray improved over his miserable start against the New York Mets last week, when the former first-round draft pick gave up seven runs without getting out of the second inning. While he was hardly crisp - needing 89 pitches before exiting with one out in the fifth - he avoided major trouble by flashing some of the talent that made Colorado take him with the third overall pick two summers ago.

The Pirates touched him for a run in the first on an RBI single by Jung Ho Kang, who later doubled home Polanco in the third to make it 2-0. A walk to Neil Walker loaded the bases with two outs but Gray zipped a 95 mph fastball by Cervelli for the third out to give the Rockies time to get to Pittsburgh's Francisco Liriano.

Pittsburgh improved to 11-0 in Liriano's last 11 starts since being on the other end of Washington's Max Scherzer's shutout on June 20, the second-longest unbeaten stretch by a Pittsburgh starter in 42 years. He eased into the fifth before Reyes lined a shot off the foul pole in left for a two-run homer to tie the game. A sacrifice fly by Marte helped Pittsburgh reclaim the lead, but Gomez tied it again in the sixth with a long solo shot to right-center, the first time Liriano has given up multiple home runs in a game since May. He left without a decision after giving up three runs and four hits, with three walks and four strikeouts.

TRAINER'S ROOM:

Rockies: 1B Justin Morneau was scheduled to play five innings Friday night for Double-A New Britain as he continues his slow return from concussion-like symptoms and a cervical neck strain. The 34-year-old four-time All-Star hasn't appeared in a Colorado uniform since going on the DL in May. ... Colorado called up LHP Jason Gurka and sent RHP Tommy Kahnle to Triple-A Albuquerque.

Pirates: RHP A.J. Burnett is scheduled to throw three innings off the mound Sunday as he continues his comeback from a flexor strain in his right elbow. Burnett worked some curveballs into the mix during a session in Miami on Thursday but manager Clint Hurdle said it's too early to tell when the 38-year-old will be available.

UP NEXT

Pittsburgh's J.A. Happ will make his fifth start for the Pirates since coming over at the trade deadline from Seattle. The 31-year-old is 2-1 with a 2.08 ERA with Pittsburgh and is 1-0 with a 1.89 ERA in four career appearances against Colorado. Rockies starter Chris Rusin is coming off the worst performance of his career, giving up 11 runs and 12 hits in a loss to the New York Mets on Aug. 22.

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