This story was excerpted from Jordan Bastian’s Cubs Beat newsletter. Dawn Klemish contributed to this edition. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

PITTSBURGH -- Adbert Alzolay clenched his right fist, hunched over and then unleashed what has become his signature, post-save fist pump on Wednesday in Detroit. It has become a familiar sight for the Cubs as they have stacked up second-half wins and moved into Wild Card position.

A major part of this surge for Chicago has been finding the right relief formula for the final few innings.

“They've done a really nice job,” Cubs manager David Ross said recently. “Finding those roles took us a minute this year.”

Bullpens are famously volatile and difficult to predict in any given season. It took until June for Ross and his staff to unlock the right recipe with the group of arms available. Some false starts for a few relievers (most notably Keegan Thompson, who was sent back to Triple-A in mid-May), combined with injury setbacks, created a complicated puzzle for the Cubs to assemble.

As the season approaches the final month, Alzolay has earned the closer’s job and is not looking back. Right-handers Michael Fulmer, Julian Merryweather and Mark Leiter Jr. have made up the main trio to set up wins. And while Leiter has been effective overall, his splitter has especially neutralized lefty hitters to the tune of a .141 average and .467 OPS, helping Chicago overcome its lack of an effective lefty option.

“It's just set everything up more for success, I believe,” said Alzolay, who has a 2.70 ERA and 19 saves in 50 games. “I feel like in the beginning of the year you were kind of like, ‘OK, am I pitching in the fourth or am I pitching the eighth?’ And then just to stay mentally locked in from the third inning to the ninth inning is really, really hard.”

Ross and his coaches needed to use the early portion of the season to learn which arms were going to emerge as the most trustworthy pieces.

Merryweather had an 8.38 ERA over his first 10 appearances, but has spun a 2.49 ERA in his 45 appearances since that rough start. Fulmer had a 7.84 ERA on May 27, but has since logged a 2.60 ERA in his last 33 outings. Alzolay had to show he could handle left-handed batters after past struggles and Leiter was looking to capitalize on his first chance as a full-time reliever for the Cubs.

Here’s a look at the Cubs’ bullpen ERA by month:
April: 3.98 ERA
May: 5.19 ERA
June: 2.65 ERA
July: 3.57 ERA
August: 4.22 ERA

There have been some minor bumps along the road, but that main quartet has held up its end of the bargain.

“We haven't had a whole lot of egos down there,” Ross said. “And then things kind of settled in when Adbert took the back-end.”

Alzolay’s save against the Tigers was his 15th within his past 20 appearances. He joins Randy Myers, Carlos Marmol, Craig Kimbrel, Héctor Rondón, Ryan Dempster and Bruce Sutter as the only pitchers in modern Cubs history to have at least 15 saves with no blown saves in a 20-appearance span.

Those post-save fist pumps should be getting even more energetic as the Cubs keep pushing for a spot on the October stage.

“It just came out,” Alzolay said of his signature move. “Everyone loved it. So we just kept doing it.”