CHICAGO -- The Cubs are still weighing whether pitching prospect Brailyn Marquez can be their October surprise. First, the North Siders wanted to give the young lefty a chance to taste the Major Leagues without the pressure of the postseason stage.

Prior to Sunday's regular-season finale against the White Sox, the Cubs selected the contract of the 21-year-old Marquez, who is the team's No. 1 prospect and the No. 64 prospect in the Majors, according to MLB Pipeline. The hard-throwing lefty has the makings of a real weapon out of the bullpen.

"For me to trust somebody, you want to get your eyes on him in real competition," Cubs manager David Ross said. "And being able to bring him into that environment, the next level, makes some sense with his stuff."

Marquez recorded two outs in the eighth inning of the Cubs' 10-8 win, but the young lefty struggled with his command and was charged with five runs. He recorded his first MLB strikeout via a 99 mph heater to American League MVP contender José Abreu, but Marquez walked three, fired two wild pitches and gave up two hits.

"I'm sure there was a lot of emotion," Ross said after the win. "It's hard to judge somebody off their first appearance in the big leagues. He got a punchout. I was happy for that. It took him a minute to settle in, which I remember my first big league at-bat or first big league start. There's so much going on."

In order to add Marquez to the 40-man roster, Patrick Wisdom was designated for assignment. Marquez has spent this season training at Chicago's alternate site in South Bend, Ind., and was recently added to the Cubs' 40-man pool for postseason roster eligibility.

While carrying a pitcher with a triple-digit fastball would make sense at any point in a season, Cubs president of baseball operations Theo Epstein wanted Marquez to shore up a few areas before getting this call to the big leagues.

Epstein said Marquez had to get back in game shape following baseball's down period. From there, it then took work for the lefty to fix his mechanics and get back to his usual performance, while honing some new pitches, including a sinker. Epstein said Marquez's showing in recent weeks pushed him to this promotion.

"I know people were calling for him earlier. He wasn't ready," Epstein said. "It was definitely a process, but we're really comfortable with where he is right now. In fact, we're excited about where he is right now. Happy for him to have this opportunity, and we'll see what happens going forward.

"I wouldn't read too much into this, except that we want to give him that inning to get comfortable. And that at least puts him on the radar screen as we move forward."

Marquez -- signed out of the Dominican Republic in 2015 -- had a 3.13 ERA with 128 strikeouts in 103 2/3 innings (22 games) between Class A South Bend and Class A Advanced Myrtle Beach last season. Over his last 12 outings, he piled up 76 strikeouts against 23 walks with a 2.01 ERA over 62 2/3 innings.

Cubs fans have been waiting to get a look at Marquez, especially given the recent promotion of lefty Garrett Crochet by the White Sox. The 21-year-old Crochet was picked in the first round of the 2020 MLB Draft, has averaged 100.1 mph with his fastball and has eight strikeouts in six MLB innings for the South Siders.

Crochet struck out Anthony Rizzo, Kris Bryant and Kyle Schwarber over two innings on Saturday night.

"That's definitely been a trend around the league," Ross said Sunday, referring to calling up young, impact arms. "You see they had a guy last night that was pretty impressive."

Whether Marquez will work his way into the Cubs' October picture remains to be seen.

"If we do what we're planning on doing and playing deep into October," Epstein said, "in some of these longer series there are no off-days. You need a deep roster of pitching. You're going to need a lot of options to get through this series with no off-days.

"So we felt like Brailyn could put himself in a position to be an option for us potentially."