PITTSBURGH -- Pat Murphy says he loves Pedro Alvarez like a son.

Alvarez, the Pittsburgh Pirates first baseman, is married to the daughter of Murphy, the San Diego Padres interim manager.

So it made for a bit of an awkward moment Monday night when Alvarez's RBI single with two outs in the bottom of the ninth inning rallied the Pirates to a 2-1 victory over the Padres.

While Murphy said he would never wish his son-in-law any ill will, he admitted it would have been better if Alvarez's second career walk-off hit would have come against another team.

"Pedro was going to be all right, though, whether that ball went for a hit or landed in one of our guys' gloves," Murphy said. "I would rather it had gone into a glove."

Alvarez gave the Pirates (48-34) their eighth win in their last 10 games and the Padres (39-46) their third straight loss.

Alvarez said he wasn't thinking about who was in the opposing dugout.

"Just trying to focus on the task at hand, which was going up there and trying to get the job done, no matter who it was," he said.

Center fielder Andrew McCutchen started the winning rally with a one-out walk off right-handed reliever Brandon Maurer (5-2). He moved to second on third baseman Jung Ho Kang's single, took third on catcher Francisco Cervelli's fly out, then scored when Alvarez grounded a single up the middle.

Righty reliever Jared Hughes (2-1) pitched one scoreless inning for the win as the Pirates beat the Padres for just the fourth time in the team's last 20 meetings at PNC Park.

Shortly after learning he had been selected to the All-Star Game for the first time in his 17-year career, 38-year-old Pirates right-hander A.J. Burnett pitched one-run ball over 7 2/3 innings for his sixth straight quality start.

"This is my home," Burnett said. "I want to represent these guys and this locker room and this city and this organization now my first time in the All-Star Game. I'm excited."

Burnett allowed five hits and three walks while striking out four. He pitched at least six innings for the 14th time in 17 starts this season.

Burnett left after giving up two-out singles to catcher Derek Norris and third baseman Yangervis Solarte in the eighth inning that put runners on the corners with two outs and the score tied 1-1. Tony Watson relieved and struck out right fielder Matt Kemp.

Padres starter James Shields' winless streak reached six games, though he allowed only an unearned run and two hits in seven innings. He struck out three and walked one while remaining stuck on seven wins since June 3.

"I didn't really have much zip on my fastball so I had to really make some pitches," Sheets said. "I used the two-seamer a lot, got a lot of outs on the sinker."

The Pirates tied it at 1-1 with a seventh-inning run on a two-out throwing error by Solarte on Alvarez's grounder that allowed McCutchen, who had doubled, to score from second base.

McCutchen was the Pirates' first hitter to reach second base.

The Padres scored their lone run on shortstop Alexi Amarista's sacrifice fly in the second inning. They have scored two runs or less in six of their last seven games and one run or less in 25 of their 86 games this season.

First baseman Yonder Alonso and second baseman Jedd Gyorko each had two hits for San Diego.

NOTES: Pirates 3B Josh Harrison was placed on the 15-day disabled list with a left thumb injury. Harrison is to undergo more testing, but a source said the team fears Harrison has a torn ligament, which likely would sideline him until late August. Harrison was injured while stealing second base in the seventh inning Sunday in a win over Cleveland. ... Pittsburgh INF Jung Ho Kang started at third base Monday and will see the bulk of the action there while Harrison is out. ... The Pirates added 1B Travis Ishikawa to the active roster a day after claiming him off waivers from San Francisco, and he struck out as a pinch hitter in the eighth inning. ... Pirates LF Starling Marte was not in the lineup a day after feeling discomfort in his left side during a fourth-inning plate appearance and leaving the game. He is considered day-to-day. ... Padres RHP Dale Thayer, who has been on the DL with a strained right shoulder since June 17, rejoined the team from his rehab assignment with Double-A San Antonio and will throw a bullpen session Tuesday before the game. ... Padres RHP Tyson Ross (5-7, 3.63 ERA) will face Pirates LHP Francisco Liriano (5-6, 2.99) on Tuesday night.