ST. LOUIS -- Jason Bay was supposed to get a breather.

Instead, his three-run, pinch-hit home run broke a tie in the eighth inning and lifted the Pirates to an 11-5 victory against St. Louis this afternoon at Busch Stadium, capping a series in which they took two of three.

It was the first pinch-hit home run of Bay's career, and he had been 1 for 11 in such situations.

"It was a good off-day," Bay said afterward, grinning.

The Pirates had trailed, 5-1, and were down, 5-4, entering the eighth when Jason Isringhausen -- who last week asked to be removed as St. Louis' closer -- was summoned to protect that lead.

He walked Doug Mientkiewicz, and Ronny Paulino singled to get it started.

Chris Gomez tried to bunt them over, but it was too sharp right back at Isringhausen and should have brought a forceout at third. But Isringhausen threw the ball into left field, allowing Mientkiewicz to trot home with the tying run.

Bay, rested for just the second time this season, sent Isringhausen's 1-2 fastball high and into the bullpen beyond left field for his eighth home run.

Off the bat, it hardly had the look of a long ball.

"I was just trying to get it in the air for the sacrifice fly," Bay said. "And that's how it felt. I hit a ball last night a lot better than that for an out. When it went over, I went, 'Wow.' "

Manager John Russell had intended not to use Bay at all, but that changed when the score tightened. He asked Bay to begin getting loose in the tunnel and indoor cage, in case he was needed, about two innings before the home run.

"It had to be the right situation, and it was," Russell said. "Obviously, he came up really big for us. It was a huge lift for us in a long game where it was wet, cold. Just huge. If you're going to get a day off and do something like that, I'd say it's even more special."

It was Isringhausen's sixth blown save, most in Major League Baseball, and third in a row.

The Pirates added three runs in the ninth off Ron Villone, one on Raul Chavez's pinch-hit single, another on Freddy Sanchez's two-run single.

The Pirates, winners of eight of their past 10, are back within a game of .500, at 20-21, heading to Chicago for a weekend set against the first-place Cubs.

They had not won a series of more than two games in St. Louis since 2003.

And this, too: The Pirates now have six victories when trailing after six innings.

"We've been doing this all year," Russell said. "We know we're in the game until it's over."

Nate McLouth gave the Pirates an early 1-0 lead with his 11th home run, lining a Joel Pineiro fastball just above the right-field fence. First base umpire Angel Campos initially ruled the ball in play, and McLouth stopped at third base, but the full crew conferred and called it correctly.

McLouth's home runs are fourth-most in the National League.

But that quickly was dwarfed by the five runs, 11 hits and a walk Ian Snell would allow in his four innings. It drizzled throughout his outing, but the lack of command was little different than what he has shown most of the season in going 2-2 with a 5.05 ERA.

Russell did not mince words when describing Snell's outing.

"You can tell he just didn't have it," Russell said. "There was no zip on the ball."

Snell had no explanation.

"I [stink}, period," he said. "I'm just trying to find my way. Baseball's funny. I'm trying to understand it, and I can't. I don't know what it is. My bullpens are great. I don't know if it's focus or what. I just know that I'm the one who got us into that mess today."

The Pirates persisted and turned that 5-1 deficit into 5-4 with a three-run fifth: Mientkiewicz, Paulino and Gomez opened with singles, the latter bringing one run. Two outs and a walk later, Jason Michaels -- taking Bay's start in left field -- sent a two-run single through the left side.

Mientkiewicz would reach base all five times up, including a hustling double, two other hits and two walks, and he made two excellent stops at the third base.

"I'm just glad to do something to help the team win," he said.

More details in tomorrow's Post-Gazette.