PITTSBURGH -- Gregory Polanco isn't an ideal leadoff hitter, especially from a statistical standpoint, as the Pittsburgh Pirates right fielder is hitting .232 with a .304 on-base percentage in 79 games.

However, manager Clint Hurdle believes Polanco is the Pirates' best option at the top of the batting order with third baseman Josh Harrison on the disabled list.

Polanco rewarded Hurdle's faith when he tripled home the winning run in the eighth inning, and the Pirates edged the San Diego Padres 3-2 Tuesday night for their fourth consecutive victory.

Polanco walked twice in the game before lining a two-out triple off reliever Joaquin Benoit (5-4) in the eighth. The hit scored left fielder Sean Rodriguez, who hit by a pitch to lead off the inning, and snapped a 2-2 tie.

"Pretty swing," Hurdle said of Polanco's game-winner. "He had some real good swings I felt throughout the night. Just a really sweet swing off a really good relief pitcher in the eighth."

Rodriguez was sacrificed to second by catcher Chris Stewart. After pinch hitter Steve Lombardozzi struck out, Polanco delivered.

"It's good for him," Hurdle said. "He's another guy that's got to settle into that mindset that I'm looking for pitches I want to hit. Once it's out of the pitcher's hand, you've got to own it."

Polanco gave the Pirates (49-34) their ninth victory in 11 games as they moved within 4 1/2 games of the division-leading St. Louis Cardinals in the National League Central. The Padres (39-47) lost their fourth straight.

"I was very excited," Polanco said. "We needed the run at that time of the game."

Left-handed reliever Tony Watson (2-1) pitched a scoreless eighth for the win, and All-Star closer Mark Melancon worked the ninth for his NL-leading 28th save.

Pittsburgh left-hander Francisco Liriano allowed two runs and four hits in six innings with six strikeouts and a walk.

Pirates center fielder Andrew McCutchen went 2-for-4 with a double to increase his hitting streak to a career-best 14 games. McCutchen hit in 13 straight in 2009 as a rookie.

After a rain delay of 1 hour, 42 minutes at the beginning of the third inning, the Padres broke a scoreless tie on right fielder Matt Kemp's two-run double to center field with two outs in the top of the inning.

Padres right-hander Tyson Ross was pulled after the delay. He worked two scoreless innings.

The Pirates got a run back in the bottom of the third when McCutchen hit an RBI double to make it 2-1.

Kemp and shortstop Clint Barmes had two hits apiece for the Padres, who have been held to two runs or fewer in seven of their past eight games.

"We've played pretty solid baseball for the most part all season, but we just seem to have a hard time finding a way to win the close games," Barmes said. "You look at this lineup and it's a little baffling why we haven't scored more runs. It's not for a lack of effort."

Third baseman Jung Ho Kang tripled in a run in the fifth inning to pull the Pirates into a 2-2 tie. The rookie's hit came immediately after Padres left fielder Justin Upton reached above the fence to steal a potential two-run home run from McCutchen.

NOTES: Pirates C Francisco Cervelli was a late scratch because manager Clint Hurdle felt he needed a game off. C Chris Stewart started behind the plate. ... Pittsburgh LF Starling Marte missed his second straight game because of a strained left oblique and was again replaced by INF/OF Sean Rodriguez. ... Padres 3B Will Middlebrooks made his first start since June 28 and went 1-for-4. He had been limited to two pinch-hitting appearances in the previous eight games because of a sore left ankle. ... San Diego C Tim Federowicz is scheduled to catch RHP Brandon Morrow's simulated game Saturday and then begin a rehab assignment next week at low Class A Fort Wayne. Federowicz has been on the disabled list since the start of the season after tearing the lateral meniscus in his right knee during spring training and undergoing arthroscopic surgery. ... The three-game series concludes Wednesday night with Padres RHP Andrew Cashner (3-9, 4.06 ERA) facing Pirates RHP Charlie Morton (6-2, 4.30).