PITTSBURGH -- David Ortiz walked to the plate representing the go-ahead run in the eighth inning, and the thousands of Boston Red Sox fans who crammed PNC Park on Friday night waited for Big Papi to send the ball over the right-field wall and into the Allegheny River.

Mother Nature and Pittsburgh reliever Jose Veras had other ideas.

A sudden -- and very brief -- downpour forced Ortiz to constantly wipe off the top of his batting helmet and Veras made Ortiz flip his bat in frustration after meekly grounding out to shortstop to help the Pirates to a 3-1 win. It provided Pittsburgh with a signature moment in a season quickly growing full of them.

"What's wrong with Mother Nature?" Ortiz said. "I just walk up to the plate and it starts pouring. What's up with that?"

Ortiz was joking. He knows Veras and the rest of Pittsburgh's bullpen had more to do with Boston's third straight loss than some rain drops.

"I thought I put a good swing on it," Ortiz said.

Veras made an even better pitch, the two runners stranded representing the last of the 11 the Red Sox left on base as Pittsburgh (38-37) crept back above .500.

"There's a time when you've got to make a decision to face a guy like David Ortiz," Veras said. "You've got to know what he does. He's a great hitter power-wise, so you've got to have a plan for those guys ... you've got to make quality pitches to that guy so that you don't pay for it."

Jose Tabata and Lyle Overbay each had two hits and an RBI for the Pirates and Paul Maholm (4-8) beat an American League team for the first time in nearly two years by surviving 5 1/3 eventful innings.

Joel Hanrahan worked a perfect ninth to pick up his 21st save in as many chances, his three easy outs capping an effective performance from five of Pittsburgh's relievers, who made a slim lead stand up by shutting down baseball's best offense over the final 3 2/3 innings.

"We had some work to do once Paul left the game, and we were able to match up well to get the guys in to face the guys that we felt that we might have had an advantage," Pittsburgh manager Clint Hurdle said. "We made the good pitches when we needed to."

Boston starter Jon Lester (9-4) pitched six solid innings but failed to become the AL's first 10-game winner, giving up three runs, two earned, while striking out five and walking one.

"I threw the ball pretty well, kept the ball down," Lester said. "Other than two hits tonight, nothing else was squared up. I'll take my chances with that every time."

Adrian Gonzalez had two hits to bump his major league-leading average to .360, but the Red Sox couldn't get the big hit when they needed it.

The Pirates and their $45 million payroll are off to their best start in a dozen years. They saw the weekend series against the Red Sox -- whose $160 million payroll nearly quadruples Pittsburgh's -- as an opportunity to make a statement.

For a night anyway, they managed to hang with the AL East leaders.

Still, the Red Sox had plenty of chances, none better than the eighth inning when two singles and a sacrifice bunt put runners at second and third with one out.

Enter Ortiz, normally Boston's designated hitter but relegated to pinch-hitter status thanks to the National League venue. The crowd buzzed when he stepped into the box, and his seven-pitch duel was as close to playoff-like atmosphere as the Pirates have seen in years.

"We had the right guy up in that situation," manager Terry Francona said. "It was a good at-bat and a tough at-bat because of the rain."

Overbay, who sat out the three-game series against Baltimore earlier in the week so he could spend more time in the batting cage to work his way out of a prolonged slump, had two crisp hits while Tabata continued his strong play as the leadoff hitter.

Maholm struggled with his command, needing 103 pitches -- including just 54 strikes -- to get through 5 1/3 innings, but he managed to keep baseball's best road team off the scoreboard.

"Paul did a very, very professional job managing traffic through the five-plus innings he was out there," Hurdle said.

Whenever Maholm found himself in trouble, he got out of it by dominating Boston's Darnell McDonald. The left fielder went hitless in three at-bats against Maholm, stranding six men on base in the process.

Francona hinted before the game he may consider playing Ortiz at first and send Gonzalez to right field during Boston's nine-game interleague road trip but opted not to take a chance on Friday because he didn't want to put any more stress on his team's already suspect defense.

Instead Mike Cameron got the start in right, but the veteran looked very much like the rookie on a flyball from Mike McKenry in the second. Cameron charged in to make the catch but misjudged the flight and the ball skipped past him, allowing the Pirates to get runners on second and third with no outs.

The miscue, officially ruled a double, helped the Pirates take a 2-1 lead.

Boston handed Pittsburgh an insurance run in the sixth after third baseman Kevin Youkilis mishandled a grounder by Matt Diaz, allowing Neil Walker to race from first to third. Overbay brought him with a single to right.

Veras, Hanrahan, Chris Resop, Daniel McCutchen and Tim Wood made sure the two-run lead was enough.

"The bullpen picked me up big, the defense picked me up big," Maholm said. "It was kind of an overall scrappy win for us."

Game notes

Pittsburgh 3B Chase D'Arnaud picked up his first major league hit with a triple to left in the fifth inning. ... The Red Sox's rained out game against Baltimore on May 17 has been rescheduled for Sept. 19. ... Boston RHP Bobby Jenks will make a minor league rehabilitation appearance on Saturday for Double-A Portland. Jenks hasn't pitched since June 7 due to a strained back. ... The game served as a homecoming for Francona, who grew up in New Brighton, about 45 minutes northwest of Pittsburgh. He estimated a couple of busloads of friends from the town were coming to the game.