DENVER -- The Pittsburgh Pirates didn't bother to stick around their clubhouse for a possible celebration after they methodically scored in succession in the early innings Tuesday night and beat the Colorado Rockies 6-3.

It's a good thing because Pittsburgh's win coupled with the Washington Nationals' loss at Baltimore meant the Pirates' magic number is one after the San Francisco Giants stayed alive with a win at San Diego late Tuesday.

Pittsburgh manager Clint Hurdle said he met with his leadership council and those players decided the team would not wait in the clubhouse for the outcome of the Giants game but return to their hotel.

"When it's official, it's official...I'd rather go home and go to bed," said Pirates center fielder Andrew McCutchen, implying his team's goals are higher than just clinching a playoff spot.

The Pirates scored in each of the first four innings, totaling their six runs in that span, all with two outs against Colorado starter Chris Rusin (5-9).

J.A. Happ (6-2), who the Pirates acquired from the Seattle Mariners for a minor league pitching prospect at the trade deadline, continued to pay big dividends. Happ (6-2) worked 5 1/3 innings, allowing three runs on seven hits with one walk and eight strikeouts. After Happ threw 82 pitches, Jared Hughes relieved him with a runner on first and got D.J. LeMahieu to ground into an inning-ending double play.

"The 82 was a lot of work out of the stretch. I've got some experience here," said Pirates manager Clint Hurdle, who formerly managed the Rockies and was their hitting coach. "You want to get your starters out of here with their sanity. I felt he battled, got us to a good part of the game. LeMahieu is a really good player and he's a very good hitter. He's hit into 14 double plays off right-handed pitchers. We've got a double play guy (in Hughes). Give him the shot at LeMahieu."

In nine starts with the Pirates, Happ has a 2.28 ERA (51 1/3 innings, 13 earned runs). He has been better than that lately, going 6-1 with a 1.73 ERA (41 2/3 innings, 8 earned runs) in his past seven games.

"I felt OK," said Happ, who yielded a homer to catcher Wilin Rosario in the second and two runs in the third. "I felt like I've had better fastball command in previous games. Definitely gave it what I had tonight. It was a battle out there. Left a few pitches over the plate. Overall felt like I kept us in there."

The win was the 91st of the season for the Pirates, their fourth straight and put them a season-high tying 31 games above .500. The Rockies fell to 2-3 on their final 10-game homestand and 1-4 against the Pirates this season.

Mark Melancon retired the side in order in the ninth and earned his 49th save, extending his franchise record. He is trying to become the seventh National League reliever to save 50 or more games in a season and the first since Craig Kimbrel (50) with the Braves in 2013. Since becoming the Pirates' full-time closer on July 24, 2013, Melancon has converted 96 of his 106 save opportunities.

"If it was a bigger city and he threw harder, there'd probably be more noise made for him," Hurdle said. "He's closing ballgames as efficiently as anybody in the major leagues. He does it with miss-hits, not big strikeout numbers. He's a pro out there."

The Pirates kept pecking away at Rusin, who allowed eight hits and four walks and needed 92 pitches to get through the fourth.

The Pirates got run-scoring doubles from Marte in the first and second baseman Josh Harrison in the second. Polanco followed Harrison with a run-scoring single. First baseman Michael Morse's broken-bat single to short center netted a run in the third.

Third baseman Aramis Ramirez and left fielder Starling Marte drove in runs in the fourth -- Ramirez with a triple off the wall in center for the 2,300th hit of his career and Marte with a slow roller that trickled into the third base bag.

"I fell behind hitters and didn't make pitches when I needed to," Rusin said. "When I get behind in the count and have to force myself to throw a strike, I either gave up hits or the balls bleeded through (the infield). Things didn't fall my way."

NOTES: Pirates 3B Aramis Ramirez left the game in the sixth due to tightness in his left groin, which he experienced rounding second while hitting a triple in the fourth. ... Rockies 3B Nolan Arenado left the game in the ninth after unsuccessfully diving for a ball and slamming his face into the ground. He suffered a contusion but passed a concussion test and will re-evaluated Wednesday. ... Rockies RHP David Hale will start Friday against the Dodgers. He takes the rotation spot of LHP Yohan Flande, who was hit on the side of the left knee with a line drive in his Saturday start and sustained a patellar tendon contusion. ... Rockies RHP Christian Bergman will start in place of LHP Jorge De La Rosa on Wednesday. De La Rosa is dealing with right Achilles tendinitis that intensified to the point where he can't start. ... Pirates OF Keon Broxton had the third base bag in his locker, a memento of his first game in the majors Monday night. He entered the game as a pinch runner in the ninth, stole third and continued home on a throwing error. ... Pirates RHP Charlie Morton, who will start Wednesday, is 3-5 with a 5.17 ERA in 10 road starts this season but has a 2.55 ERA in his past four starts away from Pittsburgh.