PITTSBURGH (AP) -- Doug Davis didn't look the way Arizona pitchers Brandon Webb and Dan Haren did the two previous days. Not surprisingly, the Diamondbacks didn't resemble the first-place team that finally appeared to be breaking out of a slide.
Jason Bay's two-run double finished off Pittsburgh's five-run fourth inning and the Pirates shook off Mark Reynolds' two home runs to beat the Diamondbacks for the first time in their weekend series 6-4 on Sunday.
Phil Dumatrait (3-3) was pulled after 5 2/3 innings on a sunny but humid 90-degree day, but still made his third consecutive effective start. He gave up two runs and four hits while walking two, and has allowed four earned runs over 18 2/3 innings (1.93 ERA) in his last three starts.
"Everybody on this team is confident when he's on the mound," said Adam LaRoche, who had three of Pittsburgh's 10 hits. "Everybody wants him out there right now."
Just as the Diamondbacks feel comfortable when they've got Webb and Haren going -- they beat the Pirates while allowing a combined four runs in 14 innings the previous two games. Davis (2-3), who has faced the Pirates more than any other major league starter, wasn't nearly as effective in his fourth start since having surgery to remove his cancerous thyroid gland.
Davis, making his 20th career start against Pittsburgh, took a 1-0 lead into the fourth only to allow six of the final eight batters he faced to reach base. LaRoche and Jose Bautista doubled to tie it at 1, and Raul Chavez -- the No. 8 hitter who reached base three times -- followed with an RBI single.
LaRoche's fly ball appeared that it would go foul, only to strike the 320-foot sign next to the foul pole. LaRoche didn't break from the batter's box until he realized the ball might drift fair, so he settled for a double.
After Freddy Sanchez's single, Jack Wilson's sacrifice fly and Nate McLouth's walk loaded the bases, Bay doubled to left to chase Davis, who surrendered five runs and seven hits in 3 2/3 innings. He is 2-5 with a 6.39 ERA at PNC Park.
"I have had struggles in the past here. I don't know what it is," Davis said. "It seems like they hit it where we're not every time."
After reliever Max Scherzer replaced Davis, Jason Michaels was ejected while arguing a called strike on a 2-0 pitch. Michaels insisted the pitch was inside, drawing a line in the batter's box to show plate umpire Jerry Meals where he believed the pitch traveled.
"He was fired up," manager John Russell said. "He's a hard-nosed player."
The problem was right fielder Xavier Nady was out for a second successive day with inflammation in his lower left leg and Russell didn't want to play him defensively. With Michaels out, Doug Mientkiewicz played in the outfield for only the sixth time in 988 career games.
Mientkiewicz inherited the 2-1 count from Michaels and walked, but LaRoche flied out to end the big inning.
Bay is 26-for-74 (.351) while getting at least one hit in 17 of his last 19 games.
"We have a lot of guys who are having tremendous years," Jose Bautista said, referring to Bay, Nady and Nate McLouth. "Now we've got some other guys starting to come around."
Arizona averaged 3.1 runs while losing eight of its previous 12 games, and the Diamondbacks didn't get much offense Sunday from anyone other than Reynolds. The only run he didn't produce came in the second, when Conor Jackson doubled and eventually scored on Chavez's passed ball.
"We've showed that we've been really good, we showed that we haven't been good at times. But you've got to stay with our guys -- our guys are our guys, and there's not a whole lot you can do about it," manager Bob Melvin said. "You've got to go with your core group, the guys who got us off to a great start and swung the bats well early in the season."
Reynolds made it 5-2 by homering to lead off the fifth, but missed a chance to tighten up the game an inning later when he grounded out with the bases loaded.
Reynolds hit a two-run drive in the eighth, his 14th of the season, following Jackson's leadoff single against Franquelis Osoria. Reynolds has three multiple home run games this season, two since May 31, and four in his career.
Matt Capps pitched the ninth for his 14th save in as many opportunities and his 32nd in 34 chances since becoming the Pirates' closer last season.
Despite the loss, Arizona is 23-14 in Pittsburgh. ... Capps' .941 save percentage since becoming Pittsburgh's closer on June 1, 2007, is the NL's best. ... Sanchez is 17-for-34 (.500) against Davis.