PITTSBURGH -- On Saturday, Mitch Keller was in command. His release point was consistent. All of his pitches were working, and he held the Cubs to just one run in five innings.

But Keller could not keep that momentum going in Thursday’s finale with the Padres, as he was quickly barreled up in the first inning en route to a seven-run outing in the Pirates’ 8-3 loss.

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After struggling with his fastball command in his season debut, Keller went to his four-seamer at one of the highest rates of his career on Thursday. Nearly two-thirds of his offerings (62.7 percent) were heaters, which is the third most by percentage he’s thrown in a start. Yet five of the nine hits he allowed came off the four-seamer, not to mention the sac fly Jake Cronenworth hit to chase Keller after 3 1/3 innings.

A big part of the reason for that was Keller's inconsistency with his breaking pitches in the first inning. After hanging a curveball that Cronenworth hit for an RBI double, Keller threw a slider right down the middle to Manny Machado, which Machado sent out for a two-run home run to give the Padres a 3-0 lead just one out into the game.

Keller’s plan was to attack, he just attacked the middle-middle zone too squarely for success.

“Those ones just kind of backed up on me and were hanging in the middle of the zone,” Keller said, “and Machado and Cronenworth are really good hitters and did what they needed to do, and they took advantage of it.

“I was all around the zone where I wanted to be, I was throwing pitches where I wanted to, just the first inning had some bad pitches there.”

This start followed an impressive five-inning outing for Keller against the Cubs in which he allowed only one run. The Chicago batters couldn’t square him, whiffing 14 times, the highest numbers of swings and misses vs. Keller since Sept. 24, 2019 (17).

Keller’s start on Saturday was also a breakthrough in regard to his command, as issued only one walk while striking out seven. It was the first time since Sept. 10, 2019, that he struck out at least that many while walking one or fewer.

But despite the results on Thursday, Keller is still encouraged by what he was able to do. He executed some fastballs above the zone that were still swatted down the line for doubles, including Tucupita Marcano’s RBI double in the first inning and Jurickson Profar’s one-out double in the second that set up a two-run frame.

“I haven’t given up two doubles down the line in a while,” Keller said, “so just all in all, kind of a bad start, but I’m still confident in myself.”

And considering Keller ended the 2020 season with an eight-walk outing, manager Derek Shelton said the fact that Keller has been in the zone a healthy amount of the time over the past two starts is reassuring. Keller threw 83 pitches on Thursday, and 53 were strikes, even though he only struck out one batter.

“I think early on it was just the sharpness of the breaking ball that got him in trouble,” Shelton said, “but I think on the flip side of it, he attacked the zone. He was in the zone, so that's encouraging.”

The Pirates are giving Keller the length to work through what he needs to, as they showed on Thursday. With the bases loaded and one out in the second inning, Shelton opted to leave Keller in with the team down by five runs because he wanted to keep him stretched out instead of pinch-hitting for him and increasing the team’s chances of getting a couple of runs back.

Time will tell if the results catch up with the progress Keller believes he’s making, but he knows the trials so far have been instructive.

“I think the only way you’re going to grow is going through some stuff like that,” Keller said, “and to be able to face their top of the lineup there for the third time in the top of the fourth inning, that’s just all experience for me."