CHICAGO -- Justin Steele walked behind the mound, lifted his left leg and winced some as he gauged if he could tolerate the pain. A sharp comebacker off Victor Caratini’s bat had struck the Cubs' lefty just above his knee, causing concern to ripple through the crowd at Wrigley Field.

“I wasn’t too worried about it,” Steele said with a shrug on Tuesday night.

That easy-going demeanor has been a steady trait for Steele, so it really did not come as much of a surprise that he shook off the second-inning scare with his aw-shucks attitude. That kind of calm played perfectly in an October-esque environment, in which Steele guided the Cubs to an important 1-0 victory.

It was the kind of gutsy performance the North Siders have come to expect from their surprising Cy Young contender. Opposite Corbin Burnes -- a recipient of that award in the National League two years ago -- Steele got back on the mound and gave his team a career-high 111 pitches over six brilliant innings.

When Steele’s night was done, he walked off the hill with a 2.69 ERA that ranks second among all qualified pitchers in baseball. He picked up his 15th win, becoming the first Cubs pitcher since Jake Arrieta in 2016 to reach that total in 25 starts or fewer. Steele’s 18 quality starts are one behind Gerrit Cole for the Major League lead.

“Just relentless, right?” Cubs second baseman Nico Hoerner marveled. “He's just always on the attack. Take a line drive to the leg and just keep going. And if anything, pick up steam.”

With the win, the Cubs pulled within four games of the first-place Brewers in the National League Central. The North Siders also maintained their hold on the second of three slots in the packed NL Wild Card race.

Outings like the one Steele fashioned go a long way in helping Chicago complete this quest for October baseball. And while the lefty has yet to pitch in the postseason, the raucous response throughout Tuesday’s clash with the Cubs’ rivals to the north brought a smile to his face in the afterglow of victory.

“I loved it. I love pitching in that environment,” Steele said. “The fans here do a really special job of knowing the situation, knowing what’s at stake, knowing when to get on their feet. I mean, I think there was a moment in the first inning they were on their feet, because they knew a big pitch was coming.”

And in the ninth, as closer Adbert Alzolay was preparing to unleash his latest wild, post-save fist pump?

“The PitchCom in my hat goes to 20 on the max volume,” Hoerner said. “I hadn't gotten past 18, but I was at 20 in the last inning -- just to be able to hear the pitch that we were going to throw. It was pretty cool. It's just amazing here.”

A hush fell over the old ballpark in that second inning, though.

Caratini’s 100.2 mph shot back up the middle hit Steele just above the left knee, but the ball caught more muscle than anything. The only issue at first was Steele having trouble putting weight on his leg. Manager David Ross and a member of the Cubs’ training staff looked on as the pitcher tested things out with a few warm-up tosses.

Was there ever any doubt Steele -- the budding ace and workhorse with an old-school mentality -- would stay in?

“I know where his heart is and who he is down to the core,” Ross said. "I wasn’t too worried."

Steele ended the evening with eight strikeouts and one walk, leaning on his trusted combination of four-seamers (62 times) and sliders (47), and growing more efficient as the night wore on. His fastball was cutting more than usual early, leading Steele to “change my sights” to recalibrate his aim.

After Steele needed 67 pitches to grind through the first three innings -- in which Milwaukee stranded six baserunners -- he tossed 44 the rest of the way. The lefty finished his outing with a run of only one hit surrendered to the final dozen Brewers batters he encountered.

“He’s a fighter every time he pitches against us,” Brewers shortstop Willy Adames said. “He always fights and tries to stay in there as long as he can, and today he was doing his best.”

It was enough to overcome a seven-inning gem from Burnes and help one first-inning run by Chicago’s lineup hold up for the win. Before the game, Ross considered the matchup and stakes and proclaimed: “This is what we sign up for.” Steele was more than up for the task at hand.

“Big-time performance by Justin,” Ross said.