Hayden Wesneski didn’t grasp his full impact until he stood on a mound in a stadium with a third deck, staring down big-league hitters.

The young Cubs right-hander excelled down the stretch last season, posting a 3-2 record and 2.18 ERA in 6 games (4 starts). Part of that was due to his best pitch — a slider that he threw 32% of the time in the big leagues.

When the Cubs acquired Wesneski from the Yankees at the trade deadline last summer, they immediately set out to try to get him to use his slider more often in games.

He finally understood why when he arrived in Chicago.

“Until last year, until it gets on TV and more guys see it, I didn’t even really know it was a good pitch,” Wesneski told Cliff Floyd in an interview on Marquee Sports Network. “I knew it was good. The Yankees were telling me, ‘hey, you need to throw it more.’ And I go to Iowa and it’s like, ‘hey, you need to throw it more.’

“All of a sudden, I get to the big-league level and you’re finally seeing guys that you’re like, ‘OK, I can throw it over and over and still have a chance.’ I finally figured out how good it actually is vs. just thinking it was a good pitch.”

It’s not like it took much convincing for Wesneski to trust in his slider. But watching MLB hitters struggle to square up the pitch — or miss it entirely — he understood what his coaches were preaching.

Now, he’s comfortable throwing the slider in any count.

“I’ve always been told: Throw your best stuff,” Wesneski said. That’s my best pitch. I gotta throw it more often.”

Wesneski threw 143.1 innings last season between Triple-A and the majors and he enters Cubs camp in competition for the final rotation spot. He could also wind up as a multi-inning reliever or even begin the year with Triple-A Iowa for more seasoning.

After his first taste of life in the majors, Wesneski set about refining his offseason program.

“Trying to get ready for a full year,” he said. “Especially at the big-league level — it’s a different game up there. Bigger, faster, stronger. I messed with some of my mechanics with stride length and trying to clean up stuff.

“As you get older, you try to make everything more refined, make it easy so you can repeat it a little easier. Every year, that’s what I try to do is make it simpler and try and throw harder.”

Check out Wesneski’s full interview with Floyd in the video above.