CHICAGO -- The Pirates will leave the Windy City winless in the past three nights, swept by the Cubs in their first brush with their division rivals this season. Given what lies ahead, the Bucs understand they can’t dwell on these three games for long. What awaits this team up north isn’t just its biggest series of the season -- it’s the club's biggest series of Derek Shelton’s managerial tenure, period.

“As soon as we get to our hotels and the sun shines the next day, this game will be out of our mind,” said Johan Oviedo following Pittsburgh’s 7-2 loss to Chicago on Thursday night at Wrigley Field. “It’s a little frustrating right now. None of us want to lose this game. But [we have a] big series coming up. We’re just excited to keep playing the way we’ve been playing. Three games won’t change anything.”

The Pirates (34-33) will enter their three-game series against the Brewers (34-34) with a half-game lead in the National League Central. The stakes are clear: whoever wins the series will own first place.

If the Pirates are going to leave Milwaukee at the top of their division, they’ll need to eliminate the back-breaking big innings that sank them in every loss. They were outscored by 17 runs over the three games at Wrigley, and in each of the three losses, they were on the wrong end of a big inning that changed the tide of each game.

On Tuesday, they allowed four runs in the seventh that turned a one-run deficit into a five-run deficit. On Wednesday, they allowed six runs in the sixth that turned a four-run lead into a two-run deficit. And on Thursday, they allowed five runs in the fifth that turned a one-run lead into a four-run deficit.

"I think that's something we've been good at over the year, just not getting too high or low,” said catcher Jason Delay. “It's kind of the game of baseball. You're going to have a good series, you're going to [have] hot streaks, you're going to have cold streaks. Just powering through, knowing that it's a long season and we're going to go through that kind of stuff."

The Brewers are in the midst of their own funk coming into their duel against the Pirates, in the midst of a season-high six-game losing streak. Milwaukee hasn’t played well on either side of the ball during its skid, allowing 31 earned runs across 53 innings (5.26 ERA) and posting a .602 OPS.

Pittsburgh will begin its three-game set against Milwaukee by sending Rich Hill to the mound. Hill, who last started on June 9, would’ve been in line to start one of the latter two games of this series, but the Pirates elected to start Osvaldo Bido on Wednesday and Johan Oviedo on Thursday and push Hill back a couple days. The rationale is simple enough: the Brewers struggle to hit left-handed pitching.

Through 2 1/2 months, the Brewers have had the worst offense in all of baseball against southpaws. Coming into Thursday, Milwaukee had the worst batting average (.216), slugging percentage (.352) and K% (28.5%) as well as second-worst on-base percentage (.292) and wRC+ (77) against left-handed pitching in the league.

Hill comes into this weekend having strung together two of his best starts of the season. On June 4, Hill allowed one run across what was then a season-high 6 2/3 innings against the Cardinals. Five days later, Hill allowed two runs and threw a season-high seven innings against the Mets.

Following Hill, the Pirates will send Mitch Keller to the mound after he had one of his better starts of the season. After allowing 15 earned runs in a three-game stretch, Keller found his form against the Mets as Andrew McCutchen collected his 2,000th hit, throwing seven innings of one-run ball with seven strikeouts.