The Pirates (60-56) helped their National League wild-card chances while hurting those of the Giants (57-59) with a three-homer assault on San Francisco pitching in a 10-5 victory in Thursday night's series opener.
The win allowed the Pirates to gain a game on the Atlanta Braves (62-50), second in the NL wild-card standings, in the eight-team fight for two spots. The Giants remained seven back.
Pittsburgh will dip into the minor leagues in hopes that right-hander Clay Holmes (1-1, 3.65 ERA) can successfully follow up on the impressive outing of veteran Ivan Nova.
Nova held the Giants to two runs on three hits in six innings Thursday, using early homers by Elias Diaz and Josh Bell as a cushion.
David Freese added his 100th career homer later in the game.
Holmes was sent to Triple-A Indianapolis despite shutting out Milwaukee on four hits over six innings in a start July 4.
He will return to the majors Friday because, Pirates manager Clint Hurdle explained, his starting rotation needs a break.
"We had this talked about after the All-Star break, planning, coming out of Colorado, the rotation," Hurdle said. "Clayton had pitched a couple games. (We're) finding a way to give guys some extra rest. This has been part of a plan for a while."
Holmes has made four major league appearances (two starts). He went 7-3 with a 3.43 ERA in 17 games (16 starts) with Indianapolis.
He has never faced the Giants, whose loss Thursday was the eighth in their last nine home games.
It's no time to panic, ex-Pirate Andrew McCutchen assured.
"These guys, they have the experience of making the second-half runs, second-half pushes, from the wild card and throughout it," he said of the Giants. "There's a sense of urgency, of course, but there isn't panic, either."
The Giants are scheduled to start left-hander Derek Holland (5-8, 3.88), who has rebounded from a stint in the bullpen with three sharp outings during which he's allowed five earned runs in 16 1/3 innings. He did not get a decision in any of the starts.
Holland propelled the Giants to a 5-0 victory at Pittsburgh in May, their only win over the Pirates in four meetings this season, with 6 1/3 shutout innings.
It was his only career outing against the Pirates.
Pittsburgh has outscored the Giants 27-17 in their four contests this season and has won eight of its last 10 in San Francisco.
The Giants hurt themselves with three errors, their most since May 29, in the series opener. One was committed by third baseman Evan Longoria, his career-high-tying 14th of the season.
Longoria and second baseman Joe Panik made errors on consecutive plays to open the seventh inning of a 3-2 game. The Pirates went onto score five runs -- four unearned -- in the game-breaking inning.