Pollock began the day in an 0-for-14 rut. He also made a diving catch in center field to rob Andrew McCutchen in the first inning.
Wade Miley (2-0) allowed two runs on five hits in 6 2/3 innings.
Jonathan Sanchez (0-2) was charged with nine runs and eight hits in 3 1/3 innings. The last two of those runs came after Sanchez left and reliever Chris Leroux walked two batters, on four pitches each, with the bases loaded in the Diamondbacks' four-run fourth.
Pollock, a long shot to make the opening day roster before spring training injuries to Adam Eaton and Cody Ross, hit a three-run homer in the second and a solo shot leading off the fourth. He had two home runs in his 81 big league at-bats last season.
Pollock, moved up to the No. 2 spot in the batting order by manager Kirk Gibson, doubled down the left-field line with one out in the first, then took off trying to steal third. Sanchez threw wildly to third and Pollock scored. Martin Prado followed with a walk, advanced to third on Paul Goldschmidt's single and scored when Miguel Montero grounded out. Alfredo Marte brought home the inning's third run with a two-out double.
Miley retired 10 in a row after Starling Marte opened the game with a double. The string ended when McCutchen walked with one out in the fourth. Gaby Sanchez singled and Josh Harrison had an RBI single.
Pollock's second homer made it 7-1. Sanchez walked Goldschmidt and gave up a one-out single to Montero Miguel, and manager Clint Hurdle had seen enough from his left-handed starter.
Leroux came on and promptly walked three straight. Another run scored on Miley's groundout and Arizona led 10-1 through four innings.
Arizona 2B Aaron Hill got a day off after being hit in the left hand by a pitch on Tuesday night. X-rays were negative and he hopes to return on Friday night. ... The Pirates, 2-4 on their road trip, return home to open a weekend series against Cincinnati on Friday. Arizona has Thursday off, then begins a three-game home series against the Los Angeles Dodgers on Friday. ... Marte had a hit to lead off all three games against Arizona. ... Pollock was 3 for 17 (.176) entering the game and hadn't gotten a hit since opening day.