PITTSBURGH -- Gerrit Cole started August leading the major leagues in wins, but the Pittsburgh Pirates right-hander hasn't won since.

Ailing right-hander Jeremy Hellickson won on the road for the first time since May and third baseman Jake Lamb homered to lead the Arizona Diamondbacks to a 4-1 victory over Cole and the Pirates on Monday night.

Cole (14-7) gave up four runs and nine hits in 6 2/3 innings with one walk and five strikeouts. He is 0-3 with a 4.70 ERA in four starts during the month.

Cole's four starts without a win matches the longest drought of his three-year career from April 15 to May 2, 2014.

"I can't put my finger on it," Cole said of his recent struggles. "The best I can do is just keep moving forward."

Hellickson (9-8) allowed one run and three hits in 5 1/3 innings while striking out four and walking one. The right-hander had gone 0-4 with an 8.67 ERA in his previous six road starts since winning May 30 at Milwaukee.

Hellickson felt ill before the game and was lifted when his gluteus muscle became cramping, the result of dehydration.

"It shows what type of pitcher he is, especially here as hot and humid as it is," Diamondbacks reliever Addison Reed said. "When it's hot, you're losing a lot of fluids and a guy isn't feeling good ... it's a great job by him."

Lamb connected for his fifth home run of the season in the fourth inning, a solo shot off Cole that put the Diamondbacks ahead 4-0 and helped snap the National League wild card-leading Pirates' four-game winning streak.

Right fielder David Peralta had two hits for the Diamondbacks, including an RBI double in a two-run first inning. He is hitting .462 (30-for-65) with 21 RBIs in his last 19 games and has a .339 batting average in 192 at-bats as the cleanup hitter, compared with .262 in his other 141 at-bats.

Closer Brad Ziegler pitched a scoreless ninth for his 21st save in 23 opportunities.

The Pirates (69-47) had their lead in the wild-card race cut to two games over the idle Chicago Cubs and dropped six games behind the St. Louis Cardinals in the NL Central while losing at home for just the fourth time in their last 19 games at PNC Park.

The Diamondbacks (58-59) improved to 14-8 in their last 22 games.

"We knew what we were up against facing Cole and playing a team that's hot in a place where they never seem to lose," Diamondbacks manager Chip Hale said. "It was a good test for us."

First baseman Pedro Alvarez had two hits and accounted for the Pirates' run with his 19th homer of the season in the fifth inning. It was the 1,000th home run hit by the Pirates at PNC Park, which opened in 2001.

Down 4-1, the Pirates loaded the bases with one out in the seventh, but Reed escaped the jam by striking out right fielder Gregory Polanco and getting left fielder Starling Marte to foul out.

The Diamondbacks jumped on Cole for two runs in the first. Center fielder A.J. Pollock tripled with one out and scored on Peralta's double before catcher Welington Castillo capped the inning with an RBI single.

"He's one of the best pitchers in the game and he has one of the best fastballs," Lamb said. "We were aggressive with the fastball and able to string some hits together in that first inning."

Second baseman Chris Owings led off the second with a double and scored on a single by Hellickson to push the Diamondbacks' lead to 3-0.

"That's a good offensive club," Pirates manager Clint Hurdle said. "We made some mistakes over the plate, they were able to put the barrel on some balls early."

NOTES: The Diamondbacks activated RHP Randall Delgado from the 15-day disabled list and optioned INF/OF Jamie Romak to Triple-A Reno. Delgado gives Arizona an eighth reliever as it is in a stretch of 21 games in 20 days before its next day off on Sept. 3. ... Pirates 1B/OF Corey Hart, who has been on the disabled list since June 22 with a left shoulder impingement and right knee discomfort, is scheduled to begin a second rehab assignment on Thursday with Triple-A Indianapolis. He was with Indianapolis from June 30 to July 11 before suffering a setback. ... Arizona RHP Chase Anderson (5-5, 4.31 ERA) will face Pirates LHP Francisco Liriano (8-6, 3.19) on Tuesday night. Liriano is 4-0 with a 3.06 ERA in eight starts since his last loss on June 20 at Washington.