They open a critical four-game set Thursday night with the St. Louis Cardinals, who seem to have finally recaptured some momentum following a lackluster stretch.
St. Louis (54-31) owns a 4 1/2-game lead over Pittsburgh (50-34), but has watched its sizable advantage diminish with six losses in the last 10 games. The Cardinals were swept in a doubleheader Tuesday but rallied Wednesday on Jhonny Peralta's two-out, two-run go-ahead home run in the ninth inning of a 6-5 victory over the Chicago Cubs.
"Any win against the division is huge for us," Michael Wacha told MLB's official website. "That homer was pretty big for us. It gives us a little happy flight going into Pittsburgh, and hopefully we can take care of business there."
The Pirates, who trailed St. Louis by nine games on June 29, have experienced no such adversity, piling up an MLB-best 32 wins since May 22. They have won five straight and matched a franchise record with their 10th sweep Wednesday, beating San Diego 5-2.
Andrew McCutchen is 6 for 15 with four RBIs over Pittsburgh's current winning streak, and the Pirates' pitching staff has posted a 2.02 ERA.
"They played so well for so long, and it just goes to show how our guys persevered," manager Clint Hurdle said. "They stayed the course, kept taking care of today's game, and it has gotten us here."
St. Louis' Carlos Martinez (9-3, 2.70 ERA) could derail that run, as the right-hander has a 6-1 record and 1.35 ERA over his last nine starts. But looking to make his final case to make the All-Star team, Martinez is facing one of the few teams who hit him hard this season.
Martinez, who is one of five players contending for the NL's All-Star Final Vote, allowed a season high-tying seven runs in 5 1-3 innings of a 7-5 loss to Pittsburgh on May 9.
"Carlos is really just getting on the map here," manager Mike Matheny said of his 23-year-old starter. "I think the fact that he's in those discussions right now is a huge compliment to him. You never know how this can play out."
Martinez will face Jeff Locke (5-4, 4.15), who is coming off the best start of his career. The left-hander yielded two hits and struck out six over eight innings of a 1-0 win against Cleveland on Saturday - his first scoreless start of seven or more innings since June 19, 2013.
"Everyone in the rotation has done it most of the season, and you never want to feel like you're the weak link," Locke said. "You want to put forth the best effort."
Locke has led Pittsburgh to a victory in four of his six career starts against the Cardinals and pitched 6 2-3 solid innings while not factoring into the decision of a 4-3 win May 10.