MILWAUKEE -- When left-hander Zack Thompson can close the gap on being the pitcher who touched 96.6 mph with his four-seam fastball early on Wednesday night, and the one who saw his velocity fall to 91.4 and 92.8 mph on hard-hit balls in the sixth inning that cost him a shot at a victory, then he can be the kind of starter the Cardinals can consistently count on, manager Oliver Marmol said.

Well aware of that fact after numerous talks with St. Louis’ coaching and strength and conditioning staffs, the 25-year-old Thompson vowed to come back next season looking more like the pitcher who shut out the Brewers over the first five innings than the one who was unable to get through the sixth.

“I know for a fact that I can get through five [innings] every outing, but now it’s about taking the next step and making sure I can get through six or seven, and get through a lineup the third time through,” Thompson said after the Cardinals’ 3-2 loss to the Brewers at American Family Field.

“I’m happy with the progress I’ve made, but not satisfied. Being able to repeat my delivery for 100 pitches will be a good starting point for next year.”

Thompson, one of the hopefuls to fill the three starting pitching vacancies the Cardinals expect to have going into the offseason, breezed through the first five innings, blanking the Brewers on the scoreboard, and recording more strikeouts (five) than hits allowed (three).

It was quite the contrast to Thompson’s two previous starts, when he allowed first-inning, three-run homers to Nick Castellanos and Josh Donaldson.

During his dominant first five innings against Milwaukee, Thompson got the bulk of his nine swings and misses off a four-seam fastball that topped out at 96.6 mph, per Statcast. However, when that velocity dipped in the sixth, William Contreras doubled off a 91.4 mph pitch that was up and Tyrone Taylor easily turned on a four-seamer that left Thompson’s hand at 92.8 mph.

Some shoddy defense certainly didn’t help Thompson in a two-run sixth when the Brewers knotted the score.

“It’s more the fluctuation between 91 [mph] and 97 [mph], and he has that ability to be more in that 94-to-96 range all the time,” Marmol said of Thompson, who was selected as the 19th overall pick by the Cardinals out of the University of Kentucky in the 2019 MLB Draft.

“He’s going to continue to improve that. We did see a tick up in [velocity] tonight, so that’s headed in the right direction. Now, it’s about the gap in the variability of it.”

Some of the fluctuation in Thompson’s pitches -- often the product of his mechanics not being properly synched up -- could be attributed to his changing role throughout his second big league season.

Thompson easily made the Opening Day roster as a reliever after not surrendering an earned run in Spring Training, and he proceeded to throw nine scoreless outings early in the season. However, when his walk rate started to climb and his fastball velocity wavered, he was hit hard and ultimately demoted to Triple-A, where he was moved back into a starting role.

More walk issues hurt him in the Minor Leagues, but Thompson got a chance to salvage his season after the Cardinals were in the uncommon place of being sellers at the Aug. 1 Trade Deadline.

When the Redbirds dealt starters Jack Flaherty and Jordan Montgomery, and relievers Jordan Hicks, Chris Stratton and Génesis Cabrera before Aug. 1, it opened up starting opportunities for Dakota Hudson, Matthew Liberatore and Thompson.

“It’s been a roller coaster of a year, but I feel like it’s made me a lot stronger, more resilient, and I’ve rounded off some of the edges,” said Thompson, who is 3-4 with 4.37 ERA in nine starts. “I’ve become more of a pitcher than a thrower and I’ve learned to just roll with the punches.

“Whatever today has for me, whatever tomorrow has or getting moved around -- just give me the ball and I’ll go pitch.”

When Thompson comes back with more bulk and consistent leg drive next season after an offseason of work, he hopes to consistently be the kind of pitcher who can use his electric velocity to blow hitters away.

“Before as a starter in years past, I always got stronger as the game went on and my hardest pitches were in the sixth, seventh, eighth and ninth innings,” Thompson said. “But moving to the bullpen and becoming more of that short-stint sprinter style pitcher, I kind of flipped.

"Now, I’ve got to get some weight back on me, be able to maintain my velocity through starts. Then, when I get in trouble and get a runner on second or third, I want to be able to really reach back and grab those [high-velocity fastballs].”