BALTIMORE -- That fantastic version of Mitch Keller that emerged in July? He showed up again for the right-hander’s first August start.

Keller was excellent once again Friday night, despite taking the hard-luck loss in the Pirates’ 1-0 defeat by the Orioles at Camden Yards. Holding the upstart O's to one run over six efficient innings, Keller thrived despite not missing many bats and came away unscathed after taking a comebacker to the right foot in his final inning.

“It hit right off the Nike logo, and nothing’s broken, so we’re good to go on that end,” Keller said. “Pitchers' duels are always fun. It just keeps you more locked in and makes you need to keep throwing up zeros.”

Watching Keller do that has been fun for the Pirates, who have seen Keller develop into the front-of-the-rotation-caliber starter they’ve envisioned for years this summer. With each outing, that breakout is looking more and more real. Keller has now completed six or more innings in each of his past six starts, posting a 2.43 ERA (10 ER over 37 IP) in those outings.

Keller had completed six innings just three times in his first 15 starts, and lugged a 5.14 ERA into July.

"[Keller] is continuing to execute pitches,” said manager Derek Shelton, who was ejected by home plate umpire Edwin Moscoso for arguing a check swing call in the eighth. “We're seeing him now with the ability to execute pitches, and he did a good job of that tonight. There was a lot of traffic. He wasn't as sharp as we've seen him. But he was able to navigate through it.”

Keller’s turnaround is inextricably linked to his sinker, which he began throwing in May to almost immediate success. That pitch was effective again Friday, resulting in 10 ground ball outs. But more notable was his curveball, which he threw 26 percent of the time, a single-game career-high.

Only two of the eight hits Keller allowed came on the curve, including the sixth-inning Ramón Urías RBI chopper that went on to be the game-winner. Meanwhile, the Pirates offense threatened several times but never broke through against winner Dean Kremer, set-up man Cionel Pérez and new closer Félix Bautista.

The loss was Pittsburgh’s MLB-high 65th decided by two or fewer runs. Eight of its last 12 games have been decided by one run.

“We got beat on a chopper,” Shelton said.

Those offensive issues distracted from the work done by Keller, a former top prospect who pitched to a 6.02 ERA from 2019-’21 and a 6.05 mark through May of this season. But he’s been a different pitcher since morphing into a sinkerballer, embracing the sinker to the point it's been his most used pitch since. Opponents are batting .303 (30-for-99) against it, but with just six extra-base hits (and no home runs).

Keller’s success has helped quell some of the Pirates’ uncertainty in their starting rotation, but it still exists, especially after the club traded veteran lefty José Quintana at the Trade Deadline. The easiest solution is probably Roansy Contreras, who struck out nine across four scoreless frames Friday night at Triple-A Indianapolis. But the Pirates have been hesitant to reinstate Contreras despite their need, citing workload concerns regarding the 22-year-old right-hander.

Perhaps that reticence will change in time, or maybe the Pirates will find a different short-term solution. But whether they are looking toward '23 or beyond, they still need innings this summer, and Keller continues to provide some of the best they’ve ever seen from him.

“I'm just looking forward to a day where I have all my best stuff and be happy to see what I can do with that,” Keller said. “The last few ones, I've haven’t had my best stuff and we've managed to go scoreless, or [a few runs]. I'm just looking forward to the day where I have my best stuff and to string it together.”