San Diego, CA (SportsNetwork.com) - A.J. Burnett had his worst outing of the season, but Pittsburgh's bats picked up the slack as the Pirates thumped the San Diego Padres 11-5 in the opener of a four-game interleague series.

Jung-ho Kang, Staling Marte and Gregory Polanco all homered for Pittsburgh, winners in a season-high seven straight games. Neil Walker, Andrew McCutchen and Francisco Cervelli had three hits and two runs apiece.

Burnett (5-1), who hadn't allowed more than two earned runs in any of his nine starts this season and came in with a 1.37 ERA, was charged with five runs -- four earned -- on eight hits in 5 2/3 innings. It was his shortest stint since his first start of the season.

Burnett still made out much better than San Diego starter Ian Kennedy (2-5), who got roughed up for seven runs in 3 2/3 innings.

The Pirates wasted little time getting to Kennedy, plating three runs in the top of the first inning on Kang's third home run of the season.

Polanco led off the second with a solo shot, Marte added a two-run blast in the third and McCutchen chased Kennedy from the game with an RBI ground-rule double with two outs in the fourth.

It was 7-0 when San Diego broke through against Burnett. Justin Upton singled, stole second and scored on Cory Spangenberg's grounder to first. Will Middlebrooks made it 7-2 later in the inning with an RBI single.

The Padres weren't done. Two errors on the same play led to Abraham Almonte scoring their third run in the bottom of the fifth, and Upton had it within 7-4 with an RBI single to center.

But Pittsburgh stole momentum right back in the top of the sixth. Cervelli singled and scored on Josh Harrison's double to the wall in left. McCutchen's two-bagger plated Harrison, and two more runners came in when Alexi Amarista's throw to third base snuck past Middlebrooks and into the seats.

Jedd Gyorko's RBI double in the home sixth provided the final margin.

Game Notes

Pittsburgh was 1-4 in its five previous interleague games this season ... The Padres had won three of four ... Pittsburgh had 15 hits to San Diego's nine.