The Pirates made a bold move by optioning Mitch Keller to Triple-A on Saturday, as he’s struggled to be effective or provide consistent length as a starter.

But Saturday’s 7-4 loss to the Brewers at American Family Field showed why one starter is far from the larger ineffectiveness of Pittsburgh’s rotation.

Chad Kuhl had to pitch in survival mode, working without his best command, to get through 3 1/3 innings on 93 pitches. The right-hander issued four walks, including two in a first inning that he escaped without harm and two in a fourth that led to four of his six runs (five earned) allowed.

Though Kuhl said he struggled with command earlier this season due to some mechanical issues, he believes the root cause of his issues on Saturday was due to the batch of baseballs.

“They were pearls,” Kuhl said. “... Tough to get your stuff to spin and stuff like that with pearls, brand new baseballs. We’ve struggled with it, and we’ll struggle with it tomorrow unless something changes.”

Baseball Savant shows his spin rate as being down across the board on all of his pitches vs. his yearly average, including a 100 rpm drop on his slider, which he throws the most of any offering. But even if this short start was a blip on the radar, the “short” aspect has still been a trend in 2021.

Kuhl has been a bit more effective at run prevention than Keller this year, even when he’s had short outings. But Kuhl (5) has only one fewer start in which he hasn’t completed five innings than Keller (6), and after Saturday’s outing, the Pirates’ Opening Day starter this season has a 6.52 ERA.

So the veteran righty has been able to navigate through innings in which a younger pitcher might struggle and lose confidence, but the bullpen has still had to run at full throttle to cover each short outing -- and these two arms are far from alone.

The Pirates’ rotation leads the Majors in starts of fewer than six innings with 52 through 63 games. In fact, they’re the only team with 50 such starts, and they’re one of four MLB rotations to have less than 300 innings on the season entering Saturday.

One saving grace for the Pirates has been two of their most reliable starters-turned-relievers who have been able to cover a lot of innings. Entering Saturday, Duane Underwood Jr. tied with Craig Stammen for the most relief innings thrown in the Majors this season at 37 2/3 innings.

Things have gotten even more taxing for Underwood recently. Three of Underwood’s past seven appearances have begun in the third inning or earlier, and three of them have also lasted three innings or longer. In 16 games prior to the recent stretch, he didn’t have to work three innings in any outing.

Tied for fourth place on that list was Chris Stratton, who was once again called into action on Saturday to bring his inning count up to 34 2/3 with a scoreless fifth. Nine of Stratton’s 25 appearances this season have been two innings or more, and four of those have come in his past six outings.

“It's just dependent on us to pick up the pieces,” Kuhl said of the starters. “We're just in a very fortunate spot that we just have an absolutely incredible bullpen, and we can't give those guys enough credit for picking us up night in and night out.”

Having the option to go to an eight-man bullpen this season, which the Pirates have used the entire time, will help the club pick up short outings. But originally, the plan was to use this setup as a measurement for arms management coming off the pandemic season.

Right now, it’s more due to ineffectiveness.

“Our starters have got to give us more innings,” manager Derek Shelton said. “We’ve got to get deeper into games with our starters. That’s extremely important because of the workload stuff with our bullpen guys.”