MILWAUKEE -- Before the lights began to strobe, before the fireworks began to pop, before the crowd began to roar, Mitch Keller stepped off the mound, walked towards home plate -- occasionally glancing towards right field -- and requested a new baseball. He knew off the bat that he’d just allowed a home run -- a three-run shot to Brice Turang that would bring Pittsburgh’s deficit to seven runs. As the ball soared, Keller couldn’t hide his disappointment.

Keller allowed eight earned runs, tying a career high, across five innings as the Pirates fell to the Brewers, 14-1, at American Family Field, their largest margin of defeat this season. For Keller, who represented Pittsburgh at the Midsummer Classic less than a month ago, Thursday’s tough outing was the latest in a string of them.

“Definitely frustrating,” said Keller, whose ERA now sits at 4.35. “Just about the only word I got."

Through his first 10 starts of the season, Keller owned a 2.44 ERA and a 2.66 FIP with 77 strikeouts in 62 2/3 innings. Per nine innings, he was striking out 11.06 batters, walking 2.01 batters and allowing just 0.72 home runs. In mid-May, Keller won National League Player of the Week honors after throwing a shutout against the Rockies, then striking out a career-high 13 batters across seven scoreless innings against the Orioles. Prognosticators billed the 27-year-old as a preliminary candidate for the NL Cy Young.

In his past 13 starts, by contrast, Keller hasn’t consistently replicated the form that earned him his first All-Star selection. He’s allowed 50 earned runs across 76 innings (5.92 ERA). The strikeouts (8.6 K/9) have been down while the walks (3.4 BB/9) and home runs (1.5 HR/9) have been up. In four starts since the All-Star break, Keller has allowed 24 earned runs across 21 2/3 innings (9.97 ERA), including two outings allowing a career-high-tying eight runs.

“It’s all about execution,” said manager Derek Shelton. “When he executes, pitches with his stuff, he has the ability to get outs.”

Keller and Shelton both pointed to the right-hander’s inability to consistently execute his cutter in recent weeks as one of his primary issues. The numbers back up that assessment.

In July, opposing hitters had a .458 batting average and an .875 slugging percentage against Keller’s cutter across 24 plate appearances. In April, May and June, by contrast, opponents had a .213 batting average and a .360 slugging percentage against Keller’s cutter.

Keller’s release point with his cutter has gotten noticeably lower compared to the beginning of the season. In April and May, Keller’s average vertical release point with his cutter was 6.01 feet and 6.02 feet off the ground, respectively. In June, it was 5.96 feet off the ground, and in July, it fell to 5.95 feet off the ground. Keller’s average vertical release points with his four-seam fastball, sweeper and sinker have lowered as well.

On Thursday, the Brewers pounced on Keller’s cutter. Turang’s home run came on a cutter that caught too much of the plate. Sal Frelick’s opposite-field, two-run double in the first inning came on a cutter that Keller left over the middle of the plate as well.

“I think that’s one of the big drivers,” Keller said. “[The cutter] just sets up everything else to lefties. That’s probably the main thing.”

Added Keller: “It’s just off. It happens. I have to get it back.”

Life won’t get any easier for Keller. As things stand, his next start will come against the Braves, a team that leads the Majors in slugging percentage (.498), OPS (.837) and home runs (206). Headlined by Ronald Acuña Jr., an NL MVP candidate, Atlanta features five position players with an OPS of at least .800 and three with an OPS of at least .900.

Keller has shown how good he can be when things are clicking. Now it’s a matter of finding the formula that earned him his first All-Star selection.