Win No. 15 has been hard to come by for Gerrit Cole, in part because of the defense behind him but also due to a dip in command.

The Pittsburgh ace takes his fourth shot at the MLB-leading victory Monday night against the visiting Arizona Diamondbacks as the Pirates try for a fifth straight win overall and at home.

Cole (14-6, 2.48 ERA) hasn't gone more than six innings in three August starts while posting a 0-2 record and 4.41 ERA after going at least seven in his previous four. He has six walks and a hit batter in 16 1-3 innings this month after issuing three walks and three hit batters in his previous 36 2-3. In Wednesday's 4-2 loss in St. Louis, the right-hander gave up at least four runs for the second time this season - three of which were earned - and seven hits in 5 1-3 innings.

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"Fastball location was sub-par," said Cole, but his manager provided some cover.

"He's had four outings in a row where we haven't defended the ball very well behind him," manager Clint Hurdle said. "Runs have been tainted throughout his outings. He pitched well. He deserved better."

Cole has been rewarded against Arizona, winning both of his career starts with a 1.98 ERA, though former NL Central foe Welington Castillo is 4 for 11 against him.

He's gone four starts without a victory one other time in his career - April 15-May 2, 2014.

Contrary to Cole, Jeremy Hellickson is coming off some of his best command of the season. Hellickson (8-8, 4.73) gave up an unearned run and seven hits in eight innings of Tuesday's 13-1 home win over Philadelphia, lasting at least eight innings for the first time in 56 starts since May 22, 2013. The right-hander, though, is 0-4 with an 8.67 ERA in his last six road starts.

Home venue didn't help him on April 26 against the Pirates as he surrendered four runs and seven hits in 4 2-3 innings of an 8-0 loss.

The Pirates (69-46) swept that three-game set in Arizona to improve to 7-3 in the series since the start of last season. Cole and the staff limited the Diamondbacks to two runs and a .189 average in the series.

Their latest three-game sweep was completed with Sunday's 8-1 win at the New York Mets to cap a 4-2 road trip, and they return to an MLB-best 15-3 home mark dating to July 4.

Aramis Ramirez was 4 for 5 with three RBIs in the finale against the Mets and is batting .375 his last 10 games.

The bullpen has also done its part with 11 1-3 scoreless innings over the last two games. Since surrendering seven runs on July 30, Pittsburgh relievers have allowed more than a run once with a 1.46 ERA over the 14-game span. The group was last charged with a loss on June 25, going 16-0 since for the major's longest run of positive bullpen decisions on record since 1914.

"They stay ready, always looking for opportunities to help, to pick the last guy up," Hurdle said.

The Diamondbacks (57-59) fell 2-1 in 10 innings Sunday in Atlanta while managing just three hits after Shelby Miller carried a no-hitter into the eighth inning. David Peralta had one and is batting .459 with 20 RBIs in his last 18 games. He's hitting .335 in the cleanup spot and .262 everywhere else to provide fine protection for third hitter Paul Goldschmidt.

"He's the guy, but he can't do everything," Peralta told MLB's official website. "That's why we're a team. The team's not about one person; it's about everybody. We're trying to help each other."