BOSTON -- During a 36-minute pregame rain delay, D-backs reliever Chad Qualls took a few slides on the slick tarp that covered the Fenway Park infield.

Later in the game, when Mike Lowell's two-run double ricocheted off the Green Monster, it was the D-backs' lead that went slip-sliding away.

Lowell's double keyed a four-run eighth inning that led the Red Sox to a come-from-behind 5-4 win over the D-backs on Tuesday night in front of a sellout crowd of 37,867 at Fenway Park.

The D-backs looked on their way to their second straight win over the Red Sox and their fifth in five attempts at Fenway in franchise history when they built a 4-1 lead through 7 1/2 innings behind starter Doug Davis.

For the third straight outing, Davis looked to be on top of his game, throwing strikes and keeping the Boston hitters off balance.

"He was carving us up pretty good," Red Sox manager Terry Francona said.

Davis allowed two hits to begin the eighth before D-backs manager Bob Melvin went to the bullpen for Qualls.

Dustin Pedroia greeted Qualls with an RBI single to right-center before the right-hander retired J.D. Drew and Manny Ramirez.

Up stepped Lowell, who had doubled to drive in two runs in his only other career at-bat against Qualls. With runners on second and third, Melvin thought about giving Lowell an intentional walk to get to the struggling Jason Varitek.

Varitek at that point had one hit in his past 31 at-bats and four in his past 47, but Melvin liked Qualls on the right-handed Lowell rather than the switch-hitting Varitek, who also was the go-ahead run.

Qualls fell behind, 2-0, and tried to go down and away with a fastball. Instead, he went down and in and Lowell made him pay with a hit that tied the game.

"Yet again, I just made mistakes tonight," said Qualls, who fell to 1-6. "It's inexcusable. Doug threw the ball way too well, we played way to well to lose this game. For us to get a lead like that in the eighth inning, we should never lose the game, so I take full responsibility. I've just got to be better than that."

Varitek then followed with a single to right to score Lowell with the go-ahead run.

"He was just missing his location," Melvin said. "The pitch to Lowell, obviously we don't want to throw a ball down the middle right there. We tried to expand away. That's what you're trying to do. On a 2-0 like that, the last thing you want to do is throw a good middle-in fastball like that to Lowell."

The Red Sox turned the ball over to closer Jonathan Papelbon, and he shut the door in the ninth to record his 22nd save.

In his last three starts, Davis has allowed four earned runs over 20 innings pitched yet has no wins to show for it. Against a tough Boston lineup, that typically wears down starting pitchers with a patient approach at the plate, Davis seemed in complete control.

"I threw strikes with all my pitches," Davis said. "If you get strike one, you can expand the zone with them. if you get strike one, then you can throw what you want and they have to hit your pitch. If you get behind them, they're going to look for one pitch and one location, and they don't miss."

Chad Tracy accounted for all the Arizona runs. In the second, he had an RBI single off Justin Masterson and then followed with three-run homer the next inning.

"He's one of those guys that is kind of funky at first when you see him," Tracy said of Masterson. "He's got good stuff, just trying to find a pitch up out over the plate that you can handle. Fortunately, I was able to get a couple out over the plate tonight."

Unfortunately for the D-backs, the Red Sox got a couple of those as well.