PITTSBURGH -- It seems there is nothing Francisco Liriano can't overcome these days, including poor command of his pitches and shoddy defense from his infielders.

The left-hander survived erratic control and shaky defense to win his fifth consecutive decision while center fielder Andrew McCutchen and first baseman Pedro Alvarez hit solo home runs as the Pittsburgh Pirates defeated the San Francisco Giants 5-2 on Sunday night.

Liriano (9-6) gave up two unearned runs in 5 1/3 innings -- the Pirates made three errors behind him, including two by Alvarez -- while allowing seven hits and three walks. Liriano struck out five in staying unbeaten in 10 starts since a June 20 loss at Washington when the Pirates were no-hit by Max Scherzer.

"I didn't get ahead in the count and I wasn't hitting my spots," Liriano said.

Liriano said the fielding miscues didn't bother him, though.

"You just focus on the next hitter if there is an error," he said. "You just have to keep making pitches after that, put it behind you and think about getting the hitters out. You've just got to stay focused."

McCutchen hit his 19th homer of the season in the sixth inning off left-handed reliever Jeremy Affeldt and Alvarez connected for his 20th off rookie lefty Josh Osich in the seventh to push the Pirates' lead to 5-2.

The Pirates (74-48) won for the ninth time in 11 games and remained 3 1/2 games behind the St. Louis Cardinals in the National League Central and three games ahead of the Chicago Cubs for first place in the NL wild card race.

Pittsburgh also won for the 20th time in their last 25 home games at PNC Park.

"Some things happened out there that complicated some things some times," Pittsburgh manager Clint Hurdle said, "but we were able to stay in front of it and gets out when we needed them and add on runs when we needed them."

McCutchen, right fielder Gregory Polanco, left fielder Starling Marte and catcher Francisco Cervelli each had two of the Pirates' 12 hits. Marte extended his hitting streak to eight games.

Alvarez drove in two runs to offset his two errors, which raised his season total to 18, most among major league first basemen.

Closer Mark Melancon pitched a perfect ninth inning for his MLB-leading 39th save in 41 opportunities.

San Francisco (66-58) stayed 1 1/2 games behind the Los Angeles Dodgers in the NL West and fell six games behind the Cubs for the second wild card. The Giants went 2-5 on their road trip to St. Louis and Pittsburgh and scored more than three runs only once.

"We were getting some help, too, and we couldn't take advantage of it," San Francisco manager Bruce Bochy said. "That was the story of the road trip, a lot of close games but not many of them went our way."

Giants third baseman Matt Duffy had three hits to run his hitting streak to seven games but grounded into an inning-ending double play in the sixth after right-hander Arquimedes Caminero relieved Liriano. San Francisco had closed to 3-2 earlier in the inning on left fielder Nori Aoki's RBI single.

Right-hander Ryan Vogelsong (9-9) lasted just 3 1/3 innings in taking the loss as he allowed three runs and seven hits while walking four and striking out two. Vogelsong had given up a combined one run in 11 innings while winning his previous two starts.

"Most of (the pitches) were starting in the strike zone and running out," Vogelsong said. "I just couldn't find a good place to start anything to keep it in the strike zone."

The Pirates struck for three runs off Vogelsong in the first inning to open the scoring. Shortstop Jung Ho Kang and second baseman Neil Walker hit back-to-back RBI singles and Alvarez followed with a sacrifice fly.

A dropped throw by Alvarez allowed the Giants to score their first run in the fifth inning.

NOTES: Pirates SS Jordy Mercer was activated from the 15-day disabled list prior to the game after being out since July 20 with a sprained left knee. He entered the game in the seventh inning as part of a double switch and went 0-for-1. 1B/OF Travis Ishikawa (strained lower back) was placed on the 15-day DL. ... Giants CF Angel Pagan, on the DL since Aug. 10 with patellar tendinitis in his left knee, played first rehab game for the Giants' team in the rookie-level Arizona League and went 1-for-2 with a single and a strikeout in five innings. ... 2B Joe Panik (lower back inflammation) began hitting off a tee Sunday at the Giants' spring training facility in Scottsdale, Ariz., and the team is hopeful he will be able to come off the disabled list Sept. 1 when the major league roster limit expands to 40 players from 25.