Ty Wiggington smashed a game-tying solo shot off Delcarmen to open the eighth. With two outs, Lance Berkman hammered a two-run double to left, giving the Astros a two-run cushion.
Before the mishap, Delcarmen hadn't allowed a run over his last 13 2/3 innings, covering a span of 12 outings that dated back to May 27.
"It's gonna happen," said Red Sox manager Terry Francona. "You certainly don't go into a game thinking, 'Well, it's been a month.' They made him work real hard. That was a long inning. They had some good at-bats. He threw Berkman a changeup that he stayed on enough. Sometimes, we got in some deep counts where good hitters, you show them enough pitches, they can stay on balls enough to hurt you."
Delcarmen had no inkling he was in for such a rough night.
"[It's] kind of tough, but that's baseball, it happens," said Delcarmen. "I just want to go out there and get them again. I felt good the whole time. You mislocate pitches, they're going to hit them. I hung that fastball up and away, and [Wiggington] just put the barrel on it and hit it well. I hung a curveball to [pinch-hitter Darin] Erstad and Berkman just sat back on my changeup. Just mislocation."
There was plenty of that on both sides. The Red Sox mounted a 13-hit attack and closed to within one in the top of the ninth, when Mike Lowell's fourth hit of the night sailed over the wall for a solo homer. But Astros closer Jose Valverde settled down, striking out Kevin Youkilis and Jason Varitek to end the game.
Aside from Lowell, the Red Sox also got a big performance from sizzling second baseman Dustin Pedroia, who went 4-for-4 with two runs and two RBIs, raising his average to .302.
"We scored 10," Francona said. "We did some good things offensively, real good. We just couldn't keep them off the board."
The Rays lost in 13 innings to the Pirates, enabling the Red Sox to hang on to their half-game lead in the American League East.
Despite producing his shakiest outing in weeks, Jon Lester (five innings, nine hits, six runs) was still in position to get the win, thanks to the Red Sox erupting for five runs in the top of the sixth to turn a 6-4 deficit into a 9-6 lead.
The big hits in that inning? An RBI triple to right by Jacoby Ellsbury, an RBI single from Pedroia and a two-run double off the bat of Youkilis.
But again, the Red Sox couldn't hang on to a sizable cushion. The Astros drew within one by scoring a pair against relievers David Aardsma and Craig Hansen in the bottom of the seventh.
Like one of those old Western movies, the Red Sox and Astros just kept firing at each other in a wild third inning. The first big hit was delivered by Manny Ramirez, who hammered a two-run double to left to break the scoreless tie. Lowell followed with an RBI double. Youkilis kept it going with an RBI single up the middle, and the Red Sox suddenly had a 4-0 lead.
The way Lester had pitched of late, that edge seemed more than safe. But the bottom of the third started bad when the lefty hit Astros pitcher Brandon Backe. After issuing a bunt single to Michael Bourn, Lester retired the next two batters and was one strike from getting out of the inning unscathed, only to give up a two-run single to Carlos Lee.
From there, bad things began to happen. Miguel Tejada hammered an infield single off Lester's left foot.
"It was my left heel," said Lester. "Kind of one of those deals, you get it in the right spot at that time and it kind of knocks for you a loop. It's fine. It's not bad right now. We'll see how it is tomorrow."
After shaking off the pain, Lester endured a different kind, giving up a three-run homer to former teammate Mark Loretta. That gave the Astros a 5-4 lead. Amazingly, all nine runs in the inning scored with two outs.
"You've got to tip your hat to Loretta," said Lester. "He was looking middle in right there and I threw the ball there. That's a pitch that I'll throw nine times out of 10. I don't regret that pitch. I was fully convicted in it, and he just put a good swing on it and hit it out. I just had to do a better job in that inning of controlling the damage and not letting it get out of hand. That was the inning that hurt me tonight."
Lee hit a towering solo homer to left in the fifth to make it 6-4.
"It [stinks] because I thought I threw the ball better than the line," said Lester. "I came out of the game, and you look up at the scoreboard, and it's 6-4 at the time. I thought I threw the ball a [heck] of a lot better than what the score said. In the fifth inning, I hang a ball to Carlos Lee and, so what? It's a solo homer; no big deal. Physically, I felt great. You've got to tip your hat to the Astros. They did a good job of hitting. The balls that I did leave up, they hit."
The Red Sox couldn't do much but shrug this one off. Lester and Delcarmen were both due for a bit of a letdown considering how hot they had been.
"We fought back, through all the mishaps tonight, to have a three-run lead," said Francona. "[We] couldn't hold it. We made some mistakes out over the plate and we about paid for every one of them."