"When you don't have that firepower, I guess, [it hurts]," said Red Sox manager Bobby Valentine. "The guys are giving great at-bats. We're just coming up a little short at times. They're wanting it real badly when they go up there, and maybe trying too hard to get the walk-off."
Then, there are those Orioles, who have reeled off wins in their last 16 extra-inning games.
"I'm tired of playing extra-inning games, to be honest with you. But we're not quitting until that last out is made, so if we need 13, 14, 15, up to 18 innings to do the job, I guess that's what we have to do," said Orioles outfielder Adam Jones.
The Red Sox are envious of what Baltimore has done.
"At the end of the season, the teams that you see going to the playoffs pull out the extra-inning games -- and win a lot of extra-inning games," said Red Sox outfielder Cody Ross. "We just haven't been able to do that this year."
It was Jones who started the winning rally when he greeted Aceves with a double into the gap in left-center to open the 12th.
Saturday was the continuation of a steep tumble for Aceves, who was Boston's closer from Opening Day until Aug. 23. The Red Sox have lost the last 11 games he's pitched in, with the righty posting a 9.87 ERA over that span. Aceves is 2-10 in 67 games this season.
"No difference in preparation," said Red Sox pitching coach Randy Niemann. "He hasn't made very good pitches. That's the bottom line. That's all I can say. There's not a lot to say. He hasn't made good pitches."
The Red Sox demoted Aceves from the closer's role in late August, also suspending him for three games at that time for insubordination.
"It's kind of like a box of chocolates right now, you never know what you're going to get, as they say," said Valentine. "You know, he's got [94-mph stuff], he's got a breaking ball, he's throwing a cutter. He's just getting hit."
Though Jones put the O's up, 6-3, with a solo shot in the top of the seventh, the Red Sox just kept chipping way.
Scott Podsednik started a seventh-inning rally with a leadoff double. Pedro Ciriaco followed with a rare walk. Dustin Pedroia reached on an infield hit, loading the bases with nobody out. Ross and Ryan Lavarnway both followed with fielder's choice RBIs, bringing Boston within a run.
In the eighth, the big hits came with two outs. Daniel Nava poked a double to left. That set up Podsednik, who drove Nava home with a double over the leap of left fielder Nate McLouth.
But the big hit that was needed for a win never came.
"It's frustrating, but we battled and had some chances, but couldn't come through -- and they did," said Ross.
It was McLouth who jump-started an O's rally in the top of the first against Red Sox starter Aaron Cook by leading off with a walk and then stealing second. He moved to third on a groundout and scored on a fielder's choice to shortstop by Jones.
The Red Sox answered quickly, as Pedroia belted a one-out double in the bottom of the first and scored on a single to right by Lavarnway.
But Baltimore jumped right back in front in the top of the second. Chris Davis hit a one-out single and moved to second on Cook's errant pickoff attempt. Machado drilled an RBI single up the middle and the O's were up, 2-1.
Mark Reynolds made it a two-run bulge in the fourth, leading off with a shot over the Green Monster.
Danny Valencia, fresh off a promotion from the Minors on Friday, answered for Boston in the bottom of the fourth, smashing a game-tying, two-run homer.
Cook got into trouble in the sixth, giving up a one-out single to Davis and a double to Machado. Valentine went to his bullpen, bringing on lefty Rich Hill to face No. 9 hitter Ryan Flaherty. That did not go well, as Flaherty ripped a two-run triple to center, putting Baltimore ahead, 5-3.
But the game came down to Aceves, who once again could not get the job done.
"He's definitely a competitor, and he's got his own style," said Lavarnway. "He kind of mixes his stuff every time ... he goes out there, so it's tough for me to pinpoint one specific thing. It's consistently different stuff. He's kind of his own animal. He goes out there and does what he can, and it ended up the cutter [didn't] quite get off the plate like we wanted it to."