PITTSBURGH -- After Caleb Kilian exited his start on June 15 against the Padres, in which he allowed five runs in four innings, the Cubs’ No. 5 prospect told reporters that he was being too fine with his pitches instead of “being aggressive and just letting it rip.”

Kilian’s first inning against the Pirates on Monday made it appear as if he was going to accomplish that goal. But in the next inning, familiar issues reared their heads, and his start spiraled out of control in a 12-1 loss to Pittsburgh at PNC Park.

In the first, Kilian put leadoff hitter Ke’Bryan Hayes into an 0-2 count with a perfectly placed fastball and curveball that clipped opposite sides of the strike zone before getting him to tip a cutter into catcher Willson Contreras’ mitt.

Bryan Reynolds flied out on a first-pitch curveball the next at-bat, bringing up Jack Suwinski, a Chicago native who hit three home runs on Sunday, to face Kilian. It became the first true battle of the night for the right-hander, as he needed seven pitches in a back-and-forth at-bat to retire Suwinski on a cutter low and away with so much horizontal break it mirrored a slider.

But the second inning began with a recurring problem in Kilian’s early MLB tenure: Walks.

Through his first two starts, Kilian had issued more free passes (seven) than he had logged strikeouts (six). He got a first-pitch strike on Daniel Vogelbach, then threw four pitches well outside of the zone to give him first. He reined in his pitches only slightly the next plate appearance against Michael Chavis, but still generated only one strike to four balls. Once again, he felt he was being a little too fine as his command waned.

“Instead of missing in the zone, I was missing just away,” Kilian said. “I was getting behind in counts [with] the walks. I just hurt myself.”

Things were already beginning to unravel, then the contact started.

The first was a grounder to second baseman Jonathan Villar, who bobbled it for an error that allowed phenom prospect Oneil Cruz to reach with an elite sprint to first base. It was a rare mishap; despite a few costly mishaps this month, the Cubs entered Monday’s series opener with only 14 fielding errors, which was the sixth-lowest total in MLB.

A single by Bligh Madris, the first of three hits in his MLB debut, put the first two runs on the board. Hoy Park knocked in Cruz from third two batters later on a fairly shallow ball, which the shortstop tagged up and scored on with a 31.5 ft/sec sprint speed (30 ft/sec is considered elite).

Kilian got a big helping hand from his defense when Jason Heyward made a spectacular leaping catch to rob Hayes and end the second inning with no further damage. But five straight batters reached on three walks, a single and a bases-clearing double by Cruz in the third inning that chased him from the game after a wild pitch scored the first run of the four-run frame.

It’s uncharacteristic of Kilian to have this many command issues -- 12 walks over only 11 1/3 innings pitched so far -- after posting a 47-to-16 strikeout-to-walk ratio in 43 innings earlier this season with Triple-A Iowa, where he had a 2.51 ERA through 10 starts in the hitter-friendly Pacific Coast League. He spent a lot of time with Chicago’s pitching group working on staying on his back leg and getting his timing right only for his outing to going short on Monday.

“It’s super frustrating, actually, because I feel like I’m digging myself in a hole,” Kilian said. “Like I said, I’m walking people, getting behind in counts. I feel like it’s not far off. I feel like it’s close. Once it clicks, it’ll be a lot better.”

With pitchers including Marcus Stroman, Drew Smyly and Wade Miley on the injured list at present, Kilian is going to get the ball on a Cubs team that is evaluating its future prospects more than it has in the past decade. Stumbles early on are common for new big leaguers, but the club hopes this run turns around to get the young pitcher’s confidence rolling.

“You’ve just got to keep working,” Cubs manager David Ross said. “That’s what it is about the big leagues. As a good buddy of mine Jon Lester used to say, ‘You’re going to have five [starts] where you’re going to be really good and nobody is going to be able hit you, and you’re going to have five where you give up a lot of runs and you stink. It’s what you do with the other 20 starts [that matters].’

“He’s got a long big league career ahead of him, and he’s a hard worker. He’ll go back to work.”