MIAMI -- The hype that surrounded Caleb Kilian's promotion to the big leagues last summer was absent this time around. The Cubs needed a starter, and the prospect was given the opportunity to show he can be trusted when such a need arises.

In a 7-6 loss to the Marlins on Saturday, Kilian showed that there is still plenty of work to be done.

"He's not ready," Cubs manager David Ross said. "He's still got learning to do, still needs seasoning."

With Jameson Taillon working his way back from the injured list -- the big righty completed a bullpen session prior to Saturday's game -- the Cubs needed a fifth starter in Miami. Kilian (No. 17 on MLB Pipeline's Top 30 Cubs prospect list) was rested and on the 40-man roster, making him a logical fill-in for the North Siders.

Things spiraled from the jump for the 25-year-old rookie, who toiled through 40 pitches and faced 11 batters in the first inning. Kilian has focused on being quicker down the mound, but things sped up too much on him and he struggled to control the immediate damage.

"I think with the adrenaline, just being in the big leagues," Kilian said, "I was a little too quick. I didn't quite catch up, so I was kind of just spraying it around the first inning."

By the time Kilian made his way back to the first-base dugout at loanDepot park, the Marlins had built a 5-0 lead. When his evening was eventually over, the righty was tagged with seven runs on 10 hits in 3 1/3 innings.

Kilian said he was "staying optimistic" about the outing, and the pitcher searched for silver linings. He ended the second with a double play and strikeout. Kilian's heater touched 97 mph, he made an in-game adjustment to rely more on his curve and had a few flashes of dominance along the way.

"The stuff's there, for sure," Cubs catcher Tucker Barnhart said. "I think I saw he was up to 96 or 97 [mph] with his fastball. Whenever you have that velo, it makes it difficult on hitters. But both of his breaking balls were really good. He was able to command the cutter after the first inning when we needed it."

Barnhart commended Kilian's efforts to "weather the storm," and the pitcher agreed that will be his biggest takeaway. His season at Triple-A Iowa has followed a similar pattern, too. Kilian was roughed up for eight runs in his 2023 debut on April 2, but responded with two solid outings (one run over nine innings combined).

"I think it's huge," Kilian said of righting things somewhat after the disastrous first inning. "Now there's something to take away, something to learn from. I didn't just go out there and completely suck. At least I turned it around a little bit."

Kilian will forever have "acquired in the Kris Bryant trade" attached to his name as long as he is with the Cubs. Acquired in 2021, the righty was brilliant that season, which he ended with six perfect innings in the Arizona Fall League championship game.

Last season, Kilian hit adversity in both the Minors and during his three-start taste of the Majors (10.32 ERA in 11 1/3 innings). He started off with a 2.06 ERA in his first nine Iowa games, convincing the Cubs to bring him to Chicago. In his final 17 Triple-A outings, Kilian's delivery went awry as he battled a left knee issue and he logged a 5.25 ERA.

"Seeing his focus and his desire to get better," Cubs vice president of player development Jared Banner said, "and make certain corrections that we deemed necessary to put himself back in a position to potentially have success again, I think has been extraordinary to watch. I'm excited about his future."

Saturday was just a reminder that Kilian still has plenty of development left on that road to the Cubs' rotation.

"Do I think Caleb's the finished product?" Ross said. "I don't think any of us believe that -- there's a long way to go. I don't think Justin Steele is a finished product, right?

"There's a lot that these guys learn at this level, going up and down, waiting for their opportunity, and continuing to grow as players."