DENVER -- Over the course of this rebuilding campaign in 2023, particularly in the second half, the A’s have been hoping to see regular development from the several promising young players who are getting their first taste of big league action this season.

Those encouraging signs can show up in multiple ways, some a bit more difficult to decipher than others. In the case of Luis Medina, the improvement has been an obvious upward trend, which continued on Sunday afternoon.

In Oakland’s 2-0 series-finale loss at Coors Field, Medina limited the Rockies to two runs on six hits and no walks with six strikeouts over 5 1/3 innings. Over his past seven outings, the 24-year-old right-hander holds a 2.97 ERA with 39 strikeouts and 18 walks across 36 1/3 innings. This follows a stretch in which Medina posted a 7.55 ERA through the first eight appearances of his Major League career.

“We continue to see a young pitcher making strides in all facets,” A’s manager Mark Kotsay said of Medina. “The mental side of the game. The competitive side. He’s showing a lot of poise. On the execution of pitches, I thought his slider was really good today. … He’s really honing in. All the preparation and work he’s done with the pitching coaches, you can see it really paying dividends right now. He threw the ball great today.”

Medina’s slider was the most impactful of his five-pitch mix. It was his most-thrown offering at 30 out of 91 pitches, generating 18 swings and a career-high 12 whiffs (swing and misses) against Colorado.

“When he has his slider going like that, you can lean on it a little bit,” said A’s catcher Shea Langeliers. “When you’ve got that going, it makes your fastball and other pitches even better. I thought he looked really good today. He attacked the strike zone and did a good job of getting ahead of guys and putting them away.”

Adding to the impressiveness of Medina's slider is how relatively new it is. When he first joined the A’s at last season’s Trade Deadline as one of four prospects acquired from the Yankees in exchange for Frankie Montas and Lou Trivino, he mostly relied on an electric fastball that frequently hits triple digits and a low-80s curveball that misses plenty of bats.

Coming off a disappointing first showing with his new organization (an 11.76 ERA in seven starts for Double-A Midland in 2022), Medina arrived at Spring Training in February and began working on integrating a slider into his repertoire. Gaining a feel for it throughout camp, Medina developed enough confidence to start throwing it in games at the beginning of the Minor League season. On Sunday, it had the makings of a signature pitch.

“Shea and I have been making adjustments in every start we’ve had,” Medina said in Spanish. “Today, we were looking for what pitch was working, and the slider was working very well. So we said, ‘Why not keep attacking with it?’ I did that and had success.”

Regardless of how many types of pitches he can incorporate, control is what will ultimately dictate Medina’s ceiling at the Major League level. His well-documented bouts with command problems throughout the Minors led to some scouts projecting him as a future reliever.

That is what makes Medina’s zero walks on Sunday even more important than his dazzling six punchouts, all of which were swinging and came on the slider. He also followed an encouraging theme from A’s pitching in this series victory. Over three games, Oakland combined to allow just six walks in 26 innings.

“To have success in this league, first and foremost, you have to throw strikes,” Medina said. “If you don’t throw strikes, no pitch will be successful. My focus has been to attack and throw strikes.

“The staff and Langeliers have done a good job in helping me figure out the abilities I have and become consistent. Shea and I have a lot of conviction in my pitches, and that has led to my success.”