The Pirates (44-48), fourth in the National League Central, play host to the first-place Milwaukee Brewers (52-42) for four games starting Monday night at PNC Park.
Pittsburgh is seven games back of Milwaukee after winning two of three in a weekend series against the third-place St. Louis Cardinals, including a 4-3 walk-off win Sunday.
The Brewers, launching a 10-game, 11-day road trip, are 11-3 their past 14 games. They began Sunday a season-best 11 games over .500 but missed a chance to sweep a weekend series from Philadelphia, falling 5-2.
Still, Milwaukee seems to be solidifying its hold on first in what has been baseball's weakest division and one seemingly up for grabs most of the season.
"I guess I'm surprised with where we're sitting with the lead," Brewers manager Craig Counsell told the Milwaukee Journal Sentinel. "I think everybody is in baseball. But I'm not surprised with how we've played. That hasn't surprised me. It's something we've fought for and had to earn."
The Pirates, meanwhile, have won seven of their past nine. How they do the next four games could determine whether they have a realistic shot at the postseason, and it could play a role in what they decide to do with the non-waiver trade deadline looming.
"We don't want to undersell, we also don't want to oversell, what this four-game series with the Brewers means," Pittsburgh general manager Neal Huntington said. "Every game's important for us, not only between now and the deadline but as we get beyond the deadline, every game matters. And that's one of the things that we need to move forward with.
"Obviously an 0-4 (series against Milwaukee) changes the dynamic pretty significant. We go 4-0, it changes the dynamic in a much more positive direction."
On Tuesday, Pittsburgh outfielder Starling Marte is eligible to return from an 80-game suspension for using performance-enhancing drugs. He is expected to be slotted in left field, with Andrew McCutchen remaining in center and Gregory Polanco in right.
"That's going to give us a boost," Pirates shortstop Jordy Mercer said of Marte's return.
Pittsburgh is 4-3 against Milwaukee this season, taking two of three at home May 5-7 and splitting a four-game set on the road June 19-22.
Left-hander Brent Suter (1-1, 2.96 ERA) is scheduled to start Monday for Milwaukee. He will be making his 11th appearance and fourth start in his fifth stint with the Brewers.
Suter made his past two starts in place of injured Chase Anderson, pitching well both times. Most recently, he gave up two runs and five hits over 6 1/3 innings, with five strikeouts and one walk, in a July 7 no-decision, a game the Brewers eventually lost to the New York Yankees 5-3.
Counsell made it clear Suter had earned more starts after the All-Star break.
"Brent was outstanding," Counsell told the Journal Sentinel. "He pitched wonderfully; it's fun to see. It's really important moving forward that we find a guy that can fill that spot and do a really nice job. There's going to be quite a few starts in that spot."
Suter has never started against the Pirates. In four relief appearances against them last season, he allowed three hits and no runs in 5 1/3 innings.
Suter will be matched against right-hander Chad Kuhl (3-6, 4.96 ERA). Pitching on two days' rest in the final game before the All-Star break as a last-minute sub, Kuhl tossed three innings of one-run ball in a no-decision against the Chicago Cubs. On July 6, he gave up three runs (two earned) in seven innings during a win at Philadelphia.
Kuhl is 2-0 with a 2.25 ERA in four career starts against the Brewers, including 1-0 with a 2.25 ERA in two starts this season.