BOSTON -- Forgive the Red Sox if they weren't keeping an open mind once Jonathan Papelbon stepped on the mound to start the top of the ninth inning on Tuesday night, a two-run lead seemingly safe and sound.

When Papelbon takes the ball with a lead, the Red Sox pretty much think the game is over. And for good reason. It almost always is.

But this time, it wasn't. With Bobby Crosby on first after a leadoff single, Papelbon left an 0-2 fastball smack in the middle of the plate, and A's rookie Travis Buck pummeled it into the box seats to the right of the visitors' bullpen in right field. Tie game, and soon, a 5-4 loss in 10 innings.

"It's very surprising," said center fielder Coco Crisp. "He's the best closer in baseball to a lot of people. It's very shocking to see him blow a two-run lead. A one-run lead, you could kind of see that happening here or there. Two-run lead, you're like, 'wow.' He'll come out tomorrow and [be] the same guy he always is, except for tonight."

And it is quite an exception when you look at the 0.92 ERA Papelbon posted last year and the fact that he had been unscored upon in his first nine outings of this season.

"It was an 0-2 pitch that I tried to elevate on him, and I left it right over the middle," Papelbon said. "I've got to do better with that 0-2, obviously, and the frustrating part about it is, you've got a guy 0-2, and he tomahawks a home run out of the park. It's a live-and-learn type of thing, and we'll get 'em tomorrow."

The Red Sox had a chance to take Papelbon off the hook in the bottom of the ninth, putting two on with one out. But Julio Lugo and Crisp grounded out to end that threat.

Brendan Donnelly couldn't get the job done in the 10th, giving up a leadoff double to center to Mike Piazza and a go-ahead RBI double just fair down the first-base line to Dan Johnson.

"I threw a bad pitch to Piazza," said Donnelly. "First pitch. Threw a bad pitch and, you know, I missed by about three feet. And he let me know about it. A leadoff double in extra innings is never a good design. Next guy, I actually thought he was actually going to bunt. When he showed he wasn't, you know, the count was in his favor. And I actually had a pretty decent pitch to him."

Just like that, the air went out of Fenway on a night when Curt Schilling (seven innings, eight hits, two runs, no walks, seven strikeouts) looked primed to notch career victory No. 211.

"The team put [me] in the situation to win, and I put that loss on my back tonight," Papelbon said. "I'll pick up the team again when they need me. It's real disappointing when you've got a starter like Curt who goes out there and performs the way he did and executes pitches and rolls over a lineup as well as he did. That's the thing where you want to pick up your teammates and pull out a win."

But it wasn't as though Schilling was going to take it personally.

"We put ourselves in that position 55, 60 times this year, we're going to win probably every other one of them," Schilling said. "There is nothing you can do about it. He'll be back in the saddle. Next time he gets in, he'll be fine."

The Red Sox had come home rolling, taking two out of three in New York to cap off an April in which they produced the best record in the Major Leagues.

But this wound up not being their night, as the bullpen, which had a 1.07 ERA in the previous 17 games, finally cooled off.

"We had the best record in the big leagues in April and I don't think we have any complete games," said Schilling. "Our bullpen has been phenomenal. No matter how well you line it up, this is the big leagues. It doesn't always work out the way you want it to."

It was clear that this was one of those nights Papelbon just didn't have it. He labored through a 35-pitch ninth and didn't strike anyone out. The last time he went a full inning without a K was last July 17.

"It's frustrating, obviously," he said. "You go out there and your team goes out there and does what they're supposed to do, gets the job done. It's just one of those things where [my] fastball command tonight wasn't good, [my] slider wasn't good and my split was OK."

The night started auspiciously for the home team with a rally in the bottom of the first. Crisp reached on an infield single and David Ortiz smacked a single to left. Manny Ramirez's sacrifice fly to right broke a scoreless tie. Kevin Youkilis roped a single to right, moving Ortiz to third. Youkilis then put himself into scoring position by stealing second.

What followed as an infield hit by Mike Lowell in the hole at shortstop turned into a nuisance for the A's. Ortiz scored from third, then shortstop Crosby committed a baseball sin by throwing behind the runner, Youkilis, who wound up also scoring to make it 3-0.

A sac fly by Youkilis in the third bumped the lead to four runs. The A's got one of those back on one swing when Johnson swatted a solo shot to right field in the fourth.

The A's were able to chip away just enough to make their efforts worthwhile. Todd Walker made it 4-2 with a sacrifice fly to center in the seventh, a play that could have scored more runs if not for a spectacular lunging catch by Crisp.

Looking back, there isn't much for the Red Sox to do but shrug off a rare mishap by their ace closer.

"We all get so used to him being almost perfect," said manager Terry Francona. "He's been so good. He's going to give up runs. You probably can't go through the year with a zero ERA. Well, he attempted to do it, but at some point you're going to give up runs."

If anyone has a closer's mentality, it's Papelbon. All he wants is the ball back in his hand with the game on the line to wash away that rare sour taste.

"For me, that's the beautiful thing about baseball," he said. "You can get back out there and go prove to your team again that you are who you are. Like I said, we have a long way to go. I'm sure down the road there will be a couple of more of these, hopefully, and I'll be able to bounce back just as well as I have in the past."