PHOENIX -- The way rookie Garrett Jones is going these days, even the balls he doesn't think are home runs wind up clearing the fence.
"He's unconscious right now, huh?" Duke said. "It seems like anything you throw him, it's off the wall or over the wall. He's fun to watch right now, that's for sure."
Jones snapped a 2-all tie in the fifth with a two-run shot that triggered a four-run rally. His line drive just went over the right-field fence after Delwyn Young's one-out single.
It was Jones' first homer with a runner on this season -- but he didn't think this one would get out.
"Honestly, no," Jones said. "I was just hoping he wasn't going to catch it."
Ryan Doumit and Steve Pearce followed with singles to chase starter Yusmeiro Petit (0-5). Brandon Moss singled home a run and Ramon Vazquez hit a sacrifice fly to make it 6-2.
The Pirates added four runs in the eighth, including RBI singles by Moss and Young, who had three of the team's 16 hits.
The 28-year-old Jones is hitting .342 with 17 extra-base hits since being called up from Triple-A Indianapolis on June 30. His 10 homers tied Donn Clendenon's franchise record for July. Ralph Kiner hit 16 in September 1949, the club record for any month.
"All hitters kind of get in that zone where you feel good," Jones said. "I'm not saying I'm there, but I'm seeing the ball well, as well as I have my whole career. I'm just trying to slow everything down. It feels good to be able to start like this."
Derrek Lee of the Chicago Cubs has eight homers this month, second-most in the majors. New York Yankees slugger Alex Rodriguez leads the American League with seven.
Jones was signed as a minor league free last winter after spending 2008 in Minnesota's organization.
A first-time All-Star this season, Duke (9-9) gave up three runs and 10 hits in 6 1/3 innings to win for the first time since June 24 against Cleveland. He struck out four and walked one.
"We kind of had him on the ropes a little bit and never really delivered a knockout punch," Diamondbacks manager A.J. Hinch said.
Ryan Roberts had two hits for Arizona, including his second major league home run. Miguel Montero had two singles and an RBI.
Ramon Vazquez, who also considered a free-agent deal with Arizona before signing with Pittsburgh last winter, had two hits and two RBI.
Petit's ERA rose to 7.68. He has not won since Aug. 23, 2008, a span of 10 starts -- nine this season as one of the fill-ins for injured ace Brandon Webb.
"He was unable to make a first pitch for a strike. That's what hurt us. You have to work ahead in the count," Montero said.