PITTSBURGH -- At some point this weekend, possibly when Cardinals rookie Zack Thompson toes the rubber against reigning NL MVP Bryce Harper or NL home run champion Kyle Schwarber, and the Busch Stadium crowd is roaring in a high-leverage spot, it will hit the left-hander just how far he’s come.

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This time a year ago, Thompson was coming off a dismal 2-10 season with a bloated 7.06 ERA at Triple-A, and he was heading to the Arizona Fall League with the mindset of “trying to figure out how to stop throwing 87 mph.”

Not only has Thompson, 24, added as much as 10 mph to his fastball at times this season, but he’s shown the toughness, fortitude and high-level stuff to likely be included on the Cardinals’ roster when the Wild Card Series opens on Friday at Busch Stadium.

Thompson has worked diligently to make the transition from a starting pitcher to a reliever, and he could be in a prime position in the days ahead while trying to retire the likes of lefties such as Harper or Schwarber in key spots. He’ll do his best to block out unnecessary thoughts, Thompson said, but it is sure to hit him at some point the monumental distance he’s metaphorically traveled in a year’s time.

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“It was a lot of days of just trying to get a little better and trusting my process,” Thompson said. “Last year, I was not where I wanted to be, and I trusted every day of the offseason and every day of the season learning how to be a reliever and trusting my preparation.”

Cardinals manager Oliver Marmol, who has been weighing his left-handed options out of the bullpen for days behind veteran Steven Matz, said he has been impressed with the aggressiveness of Thompson.

Some three hours before the first pitch of Wednesday’s regular-season finale -- a 5-3 Pittsburgh defeat of St. Louis -- Marmol had left-handers Génesis Cabrera, Packy Naughton and Thompson on the mound competing, theoretically, for a playoff roster spot. Those three were tasked with pitching against veteran catcher Yadier Molina, injured outfielder Tyler O’Neill and rookie Nolan Gorman.

In Thompson, the Cardinals saw a fiery competitor who wasn’t about to back down from a challenge, Marmol said.

“Thompson showed us what we wanted to see from him,” Marmol said following Game 162, as he was shifting his focus forward toward the playoffs.

Hearing that support from his manager meant everything to Thompson, because if there’s one thing he’s learned in the past few months, it’s that Marmol doesn’t hand out compliments carelessly, and he means what he says. He liked Marmol putting the three lefty relievers in the spotlight and under pressure on Wednesday to battle for a playoff spot.

“[Marmol’s trust] means a lot, because that guy sees through all the crap. It really means a lot that he trusts me,” said Thompson, who is 1-1 with a stellar 2.08 ERA in 22 games this season. “Competition is what we’re here for, and I like the competition. I love competing with this team, because it’s an awesome group in this [clubhouse].”

It was during Wednesday’s lefty competition that Thompson again thought back to last season’s predicament, when he was languishing in the Minors and trying to figure out why his pitches were losing so much steam.

This season, while working closely with pitching coach Mike Maddux and taking tips from closer Ryan Helsley, Thompson was able to unlock some of his missing velocity. Helsley, a first-time All-Star in 2022, is a good person to talk to about velocity, with him throwing MLB’s fastest pitch on three different occasions and finally topping out at 104.2 mph on Sept. 27 in Milwaukee.

Now with a fastball that has topped out at 98 mph and averages 95 mph, Thompson feels well equipped to face the likes of Harper and Schwarber.

“Velo is never a bad thing to have a little extra of,” said Thompson, who has thrown his fastball 54 percent of the time and his curveball 31 percent of the time. “Some days, you’ve got to get by without [your top velocity]. Some days, it’s nice to have that extra weapon and know you can blow it by some guys if you need to.”

If the rookie finds himself in a big spot, facing a powerful lefty such as Schwarber, Thompson said he will do his best to control his emotions so he can continue to perform at a high level. Lefties hit just .146 off him this season, and he wants to continue that.

“I had a talk with [infield coach] Stubby [Clapp] during BP, and he said, ‘Nothing changes in the postseason,’” Thompson recalled. “It might be a little louder, but the game doesn’t change, and my process doesn’t change. I’m just going to attack it like any other day if I’m a part of that roster.”