Jason Giambi hit a two-run homer into the upper deck in the 10th inning, and the Yankees rallied past the Pittsburgh Pirates 7-5 last night with help from a questionable call at first base.

Jorge Posada tied the game with a two-out double off Jose Mesa in the ninth, and New York overcame Kevin Brown’s latest back injury to beat Pittsburgh for the second straight night.

After the unveil ing of the plans for a new $800 million stadium, the Yankees summoned some of their old late-inning magic.

Trailing 5-4, New York caught a big break in the ninth. With one out and a runner on first, Gary Sheffield’s smash up the middle appeared headed toward center for a single. But it deflected off Mesa (0-5) to shortstop Jack Wilson, who tried to start a double play that would have ended the game.

Replays clearly showed the relay from second baseman Jose Castillo beat Sheffield at first, but he was called safe by umpire Tony Randazzo.

Pittsburgh’s middle infielders protested a bit, though manager Lloyd McClendon never came out of the dugout to argue.

Alex Rodriguez followed with a single, and Posada doubled to tie it. When the throw in trickled away from Wilson, Rodriguez made an ill-advised decision to try and score. He was easily cut down at the plate.

Not to be deterred, the Yankees got a leadoff walk from pinch-hitter Tino Martinez in the 10th.After Tony Womack sacrificed, Giambi drove a 2-2 pitch into the right-field upper deck to win it.

It was the first moment of pure elation in a long while for Giambi, booed loudly after striking out in the eighth. His third career game-ending homer – second with the Yankees – made New York 1-30 this season when trailing after eight innings.

It also was his first homer since May 17 in Seattle, and he took a curtain call to celebrate.

Mariano Rivera (3-2) pitched two scoreless innings for the win.

The Pirates got home runs from Jason Bay and Wilson, and Mark Redman shut down the inconsistent Yankees for 6 2 /3 innings.

Brown left in the fifth inning with lower back spasms. He will be re-evaluated today. The right-hander gave up RBI singles to Bay, Ryan Doumit, and Daryle Ward, and the Pirates built a 4-1 lead for Redman, who entered with a 2.80 ERA. Backed by three double plays, he allowed two runs and nine hits.

The Yankees cut it to 5-4 in the eighth on Hideki Matsui’s RBI single and Ruben Sierra’s run-scoring double off Mike Gonzalez. But with a runner on second and one out, Gonzalez struck out Giambi, drawing boos from the crowd of 48,828. Gonzalez then got Robinson Cano to ground out.

Wilson homered on the first pitch from Tanyon Sturtze in the seventh, and Bay did the same in the eighth, making it 5-2.

Posada also connected for the Yankees, and Cano had an RBI infield single.

Brown allowed three runs and seven hits in 4 1 /3 innings. He struck out six and walked one. Brown missed his previous turn in the rotation because of a sore left shoulder. He got hurt while covering first base in Minnesota on June 5. He missed the first two weeks of the season with a strained back.

Coming off a 3-9 road trip, the Yankees have won consecutive games for the first time since a five-game winning streak from May 22-27.