SAN DIEGO -- All Derek Norris wanted to do in the ninth inning at Petco Park on Friday night was put the ball into play.

"That was unfamiliar territory for me tonight," the San Diego Padres catcher joked after making major league history.

For Norris, who had struck out in his first four at-bats, hit a two-out, walk-off grand slam to give the Padres a 6-2 win over the Pirates, ending Pittsburgh's seven-game winning streak.

Norris' bases-loaded shot into the Padres bullpen beyond left-center marked the first time in major league history that a player hit a walk-off grand slam after striking out four times.

It was the sixth, walk-off grand slam in Padres history and the second grand slam of Norris' career. It was also the Padres' first walk-off win of the season.

"Walk-off wins are big boosters for clubs," said Norris.

Norris' blast came off Pirates right-handed reliever Rob Scahill, who was one out away from getting out of a bases-loaded, no-out jam in the ninth. The two hitters before Norris -- pinch-hitter Alexi Amarista and first baseman Yangervis Solarte -- had both grounded into force outs at home against a drawn-in, five-man Pirates' infield.

Scahill missed with his first pitch to Norris, then left a slider up.

"He didn't want to fall behind 2-and-0," said Norris. "I knew it was going to be a strike. I caught it pretty good. This is one of those things you dream about as a kid."

"It was a bad pitch," said Scahill. "But that's not what cost us the game. It was my throw to first. That's it. I messed it up. Nobody feels worse than me. I got the ground balls I needed. But if I make the throw, the inning is over."

Padres second baseman Jedd Gyorko drew a walk from Scahill to open the ninth. Center fielder Abraham Almonte then sacrificed on a bunt to Scahill, who fielded the ball but threw wild to first allowing Gyorko to reach third and Almonte second with no one out.

"I just babied it," Scahill said of the throw. "I've made that throw thousands of times. I just babied it and threw it away."

Scahill then walked third baseman Cory Spangenberg to load the bases with none out.

But the Pirates, deploying a five-man infield, got two straight forceouts at home before Norris hit his fourth homer of the season.

"Norris has a lot of grit," said Padres manager Bud Black. "He rises up at crucial times. You don't see that often."

Right-handed closer Craig Kimbrel (1-1) got the win with his first 1-2-3 outing in his last eight appearances. Scahill (1-3) suffered the loss.

The Padres had tied the game at 2-2 with two runs in the seventh after being shut down over the first six innings by Pirates starter Francisco Liriano.

Liriano shut out the Padres on three hits and a walk while striking out 11 in six innings -- giving him 23 strikeouts in 12 innings over his last two starts.

But as soon as Liriano departed, the Pirates were in trouble.

Right-handed Pittsburgh reliever Jared Hughes walked the first hitter he faced then gave up an infield hit to Gyorko. Almonte followed with a two-run double to the wall in left center to tie the game.

But the Padres couldn't get the go-ahead run home from second with no one out. Almonte was sacrificed to third but caught in a run-down on pinch-hitter Will Venable's grounder to a drawn-in first baseman Pedro Alvarez. Right-handed reliever Arquimedese Caminero struck out Norris to end the inning with the game tied.

The game-tying rally allowed Padres starter James Shields to keep his umblemished 6-0 record. Shields allowed two runs on six hits, two walks and a hit batter in six innings.

The Pirates took a 2-0 lead in a strange third inning when left-handed-hitting first baseman Pedro Alvarez beat the defensive shift, grounding a two-out, bases-loaded single through the spot normally manned