MESA, Ariz. — There’s trial by fire, and then there’s debuting in the midst of a push for a playoff berth.

“I loved every second of it because every pitch mattered,” Cubs rookie Jordan Wicks said of his introduction to the major leagues. “… You get that self confidence out of it. And, OK, this is stuff I need to work on, but my stuff is good enough to compete at this level.”

The lefty is set to start the Cubs’ Cactus League opener against the White Sox Friday, manager Craig Counsell announced Wednesday. He entered this spring, in major-league camp for the first time in his career, with a sense of calm that can only come from an overall successful first stint in the big-leagues.

Wicks is in the mix for the fifth rotation spot, along with Drew Smyly, Javier Assad and Hayden Wesneski.

“I feel like I still have a lot to prove,” Wicks said in a conversation with the Sun-Times. “I feel like I’ve still got to keep getting better each and every day. I like the idea that coming into camp there’s a little bit of competition for that spot. Just because I feel like it makes all of us better. Nobody can relax, we’re all trying to get the best out of each other. Because, at the end of the day, that’s what makes the team better and puts us, as a team, in the position we want to be in.”

Over the offseason, Wicks worked on staying over his back leg a little longer and really using his legs. He noticed his mechanics had slipped a little toward the end of the season, which may have stemmed from fatigue.

He also focused on reviving his slider. In 2022, he tweaked the pitch to give it sweeping action. Then in 2023, he began the season in Double-A, where MLB was testing a tackier ball.

The “enhanced grip” ball experiment in the Southern League came in the wake of MLB’s 2021 sticky stuff crackdown. They were looking for an alternative that gave pitchers a little more grip, while still banning use of foreign substances. The tacky balls enhanced some pitchers’ stuff, but Wicks was thrown off.

“I felt like I had to change something every three days with that,” he said. “So that just kind of messed up my slider for the rest of the season. I didn’t have any consistency.”

The Cubs promoted Wicks to Triple-A in late June, getting a regular baseball back in his hand. He got the call-up to the big-leagues less than two months later, sliding right into the rotation.

“I wasn’t a huge fan of minor league baseball, because your sole focus is your own development,” he said. “And that’s not how I was brought up [when it came to] coaching. So it was really difficult for me to flip that switch. But it was a lot more normal being up here where we’re really worried about winning the game, and that’s what matters.”

Wicks was dominant in his first four major-league starts, posting a 1.99 ERA. The Cubs won all four games. Then Wicks gave up three runs to the Diamondbacks and Rockies each and threw a clunker in Milwaukee. He threw just 24 sliders in the majors, accounting for about 4% of his pitches.

“At the end of the year, you’re coming up, we want you to use your strengths and be able to pitch off of what’s gotten you to that point,” pitching coach Tommy Hottovy told the Sun-Times. “The offseason allowed him to not only work on some mechanical things he wanted to work on, but also hone in that slider and make it a weapon, and one I think we can really utilize.”

Wicks’ slider shape has been much more consistent this spring, according to Hottovy. And he’s comfortable throwing it to both right- and left-handed hitters.

“It’s definitely going to have more sweep,” Hottovy said, “and it’s going to separate so much off of his curveball, too, which is going to be nice.”