PITTSBURGH — Brad Keller broke into the Royals’ rotation in late May after spending the first two months of the season in the bullpen. He’s only solidified the role in 19 starts since, becoming one of the most dependable arms on Kansas City’s staff.

The rookie right-hander wasn’t as sharp as he would’ve liked early on in the Royals’ 7-6 loss to the Pirates at PNC Park on Monday, allowing runners in the first four innings. Keller described this outing as a battle, but he settled in after making adjustments and finished with seven strikeouts while allowing four runs over six-plus innings.

Keller departed with a lead, but was saddled with a no-decision as the Pirates won in walk-off fashion on Jacob Stallings’ RBI single to left field in the ninth inning.

“I obviously didn’t have my best command today, especially early on,” Keller said. “But the changeup started to come on late, so I tried to roll with that. I felt like I had a few more innings, and then that seventh inning — base hit up the middle and then kind of a cheap hit right there got me out of that game. But definitely a grind one.”

Keller, 23, was originally drafted by the D-backs in the eighth round of the 2013 Draft. After spending his 2017 season with Arizona’s Double-A Jackson affiliate, the right-hander was selected by the Reds in the Rule 5 Draft last December before being immediately dealt to the Royals.

Keller has been especially good over his past seven starts, posting a 4-1 record with a 2.40 ERA. He’s been efficient with his pitch count as well. Monday was the fourth straight start in which he completed six or more innings, and the 11th time he’s done so this season.

“He got us into the seventh. Did a great job by doing that,” Royals manager Ned Yost said. “[He] threw the ball really, really well. … I thought he put us in a position to win.”

Working with a one-run lead in the third inning, Keller served up a out-out single to Adam Frazier, who scored on Corey Dickerson’s RBI single to left field. Frazier later broke the tie when he drove in a pair with a long double to right field in the fourth.

The Royals used a small ball approach to rally against Pirates right-hander Joe Musgrove in the fifth inning. Kansas City strung together four singles — including RBI knocks by Alex Gordon and Salvador Perez — to tie the game before Ryan O’Hearn’s RBI double and Jorge Bonifacio’s sacrifice fly opened a 5-3 lead.

Keller pitched a perfect fifth inning and worked around a two-out single in the sixth. Clinging to a two-run advantage, he returned to the mound for the seventh despite having thrown 99 pitches.

“I felt good,” Keller said of the decision to pitch beyond the sixth. “And then obviously Ned asked me if I felt good going into the seventh inning, and I said, ‘Yeah.'”

Keller didn’t last long in the inning. He gave up back-to-back singles to Pablo Reyes and Starling Marte, ending his night as left-hander Tim Hill took over. Hill gave up an RBI single to Josh Bell to cut the Royals’ advantage to 5-4, but got out of the inning with the lead.