Collmenter (1-3) lasted six innings, yielding three runs and six hits while striking out three.
"I was all over the place the first couple of innings. I was throwing, not pitching. I had a bad pitch to Harrison and that was probably the difference in the ballgame," Collmenter said. "You don't want to tax the bullpen and get out of there in just a couple of innings. You just continue to go out there and usually find a groove."
Cole (3-0) allowed one run and seven hits in 7 2-3 innings and was hitting the high 90s (mph) on the radar gun even toward the end of his outing. He struck out seven and walked two, improving to 7-0 since Sept. 7 last season.
"I just kept a good delivery throughout the game and tried to stay in a good rhythm," Cole said. "Just kept trying to stay aggressive."
The Diamondbacks got down by three runs early and couldn't come back.
"He was throwing a lot of first-pitch strikes and guys were behind in the count," Arizona slugger Paul Goldschmidt said of Cole. "As hard as he throws it and with the good off-speed stuff he has, it's hard to recover from that."
Harrison lined a two-out double to right-center in the second inning off Collmenter, driving in Jordy Mercer and Cole to give the Pirates a 3-0 lead. Pittsburgh scored all its runs with two outs.
Walker's RBI single in the first gave him a seven-game hitting streak, the longest for any Pirates player this season. Walker also doubled in Andrew McCutchen from first base in the eighth.
Goldschmidt beat Walker's throw home from second base on an infield hit by Chris Owings with two outs in the sixth for the Diamondbacks' only run.
Mark Melancon pitched the ninth for his fourth save. The Pirates have their second three-game winning streak of the season.
ZIEGLER TIES RECORD
Diamondbacks reliever Brad Ziegler tied a club record with his 253rd appearance when he entered in the seventh. Ziegler matched Jose Valverde's mark.
Arizona's starting pitchers have a 2.17 ERA over 54 innings with just one home run allowed in the past eight games.
Pirates: OF Starling Marte was back in the lineup after being limited to pinch running in Thursday's win over the Chicago Cubs in Pittsburgh. Marte left Wednesday's game with a bruised right hand after being hit by a pitch. He went 1 for 4 on Friday. ... INF Justin Sellers, on the disabled list with left heel pain, is on a rehab assignment with Class A Bradenton.
Diamondbacks: Arizona pitchers Patrick Corbin and David Hernandez, both coming off 2014 elbow surgery, are working their way back. Corbin was scheduled to throw a bullpen session Friday at Chase Field, and Hernandez is slated to throw in an extended spring training game at the team facility in nearby Scottsdale on Saturday morning.
Pirates: RHP A.J. Burnett has received just three runs of support in his first three starts. He gets the ball Saturday against Arizona.
Diamondbacks: Rubby De La Rosa will face the Pirates for the first time in his career.
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