PHOENIX -- Asked about facing former Pittsburgh Pirates teammate Zach Duke prior to Saturday's game, D-backs first baseman Adam LaRoche admitted he had very few trade secrets to share in Chase Field's home clubhouse. Then, as if foreshadowing fate, the lefty-hitting LaRoche praised Duke up and down and added, "He's pretty tough against righties, too."

It showed. Surprising the 22,400 patrons present Saturday, Duke (2-0) bested Arizona ace Dan Haren (1-1). The D-backs mustered three late-inning runs but proved unable to overcome an atypical Haren outing -- six runs (five earned) on nine hits over 6 2/3 innings -- and dropped their second game of the 2010 season, 6-3.

"It was one of those without my best stuff," explained Haren, five days following his Opening Day gem. "I wasn't able to put up as many zeros as I usually can."

The D-backs aim for the series victory Sunday afternoon when No. 2 starter Edwin Jackson counters the Pirates' Daniel McCutchen, whose start had been delayed a day, meaning Duke pitched Saturday on four days' rest.

As it pertains to the D-back's season-long ambitions, Haren's 108-pitch effort indicates more than a properly built-up pitch count. With co-ace Brandon Webb (throwing shoulder) on the mend -- Webb will play catch Monday to restart his throwing program -- the D-backs are even more dependent on one of two All-Star right-handers who is healthy.

In 2009, the D-backs went 19-14 in Haren's starts and 51-78 in games started by other pitchers. Haren is undoubtedly important to their plans this season, and he knows it. He also recognizes he'll have plenty more opportunities in 2010.

"It's no big deal, it's so early," Haren said of his shaky nine-strikeout performance Saturday.

The Pirates got to Haren early Saturday, grabbing a 1-0 lead in the opening inning when Lastings Milledge singled home Aki Iwamura, who had led off the game with his own base hit. Jeff Clement's second-inning line-drive home run on a 1-0 Haren heater increased the D-backs' deficit to two.

Haren struck out the side in the third by leaning on his off-speed repertoire but found more trouble in the fourth. Ronny Cedeno plated his team's third run on a double to left field and the ensuing batter, Iwamura, pulled and lifted a two-run home run over the right-field fence, making the score 5-0.

"I left a lot of balls out over the middle of the plate, too many pitches up in the zone, and that's not a recipe for success," said Haren, who admitted he was fighting his own mound mechanics. "Most of the damage was done on the fastball [and] cutter."

All that said about Haren, and the offense didn't exactly pick him up. One night after producing nine runs against Pirates starter Charlie Morton and the three relievers cleanup man LaRoche and Co. managed just three, tying their lowest output of the five-game season.

"I don't think he threw too many curveballs or sliders, and that's his best pitch," said Conor Jackson, who went 0-for-2 with two walks. "He was just fastball-changeup, and he threw a lot of two-seamers, keeping them down."

Aside from Mark Reynolds' two-run, seventh inning home run -- his second blast of 2010 traveled 476 feet and landed on the second deck beyond left field -- the D-backs repeatedly stood stifled in the batter's box. Duke induced 12 groundouts (including two double plays) over his seven-inning start; he allowed just four hits.

Down 6-2 in the eighth, however, Arizona cobbled together one significant threat against a triumvirate of Pirates relievers. Kelly Johnson led off the frame with a double -- he advanced to third on a Pirates error -- and pinch-hitter Rusty Ryal and Jackson drew walks, loading the bases with no outs for Tony Abreu, the potential game-tying run.

Abreu's sacrifice fly to center field brought Johnson home for the D-backs' third run of the game, and a second Pirates error put men on second and third base with one out for, of all alternatives, Arizona's Nos. 3 and 4 hitters.

Before Javier Lopez whiffed LaRoche, however, Brendan Donnelly battled and eventually K'd Justin Upton, too.

"Justin had one pitch to hit and fouled it off," manager A.J. Hinch said. "And Donnelly executed a couple of good pitches on him and got him to chase. Donnelly beat Upton. They won that battle."