CHICAGO -- Twice on Tuesday morning, when discussing rookie lefty Justin Steele, Cubs manager David Ross reached back to a moment in early May. The pitcher had escaped an extra-inning jam against the Dodgers and came off the mound flexing and shouting.

"He kind of was screaming and raging coming off the field," Ross said. "I still smile every time I've got that image in my head."

• Box score

Ross said moments like that one can show a young player that he belongs in the big leagues. Now the Cubs are seeing if Steele belongs in their rotation. That evaluation process began in a 4-2 loss to the Brewers in Game 1 of Tuesday's day-night doubleheader.

Following a stellar stint as a starter with Triple-A Iowa -- giving Steele time to build up his pitch threshold -- the lefty made his MLB starting debut against Milwaukee. Steele was sharp the first time through the order, but then experienced some more "growth moments" as his five-inning outing progressed.

“I looked at it as just a great opportunity. I was blessed with it,” Steele said. “It means the world to me to get out there and start for the Chicago Cubs. It's something I've been dreaming of my whole entire life. I'm just glad it's finally here and it's happening. It's just a true blessing.”

In the fourth inning, Steele tried to spin an 0-1 slider over the outside edge of the zone, and Willy Adames sent it out to right field for a game-tying homer. Two batters later, Avisaíl García crushed an elevated sinker a projected 457 feet (per Statcast) to the bleacher seats in left-center.

It was a rough three-batter sequence -- Eduardo Escobar delivered an opposite-field double between the blasts -- that prompted a quick mound visit from pitching coach Tommy Hottovy. Eight pitches later, Steele had recorded three outs to limit the damage.

Recovery moments like that will be a part of Steele's development over the next seven weeks.

"We're just excited to get our hands on him in more of a one-on-one personal [setting]," Hottovy said prior to the game. "The starter relationship is way different than a reliever one. Being able to work on things during bullpen days and having time to continue to refine things, I think, is an important part of his process.

"I'm just excited to see him go out there and go two or three times through a lineup, and just continue to attack with some plus-plus stuff."

Hottovy noted that the 26-year-old Steele did "everything he needed to do" during his trip back to Iowa to show that he could be a starter. In five starts at Triple-A, he fashioned a 0.87 ERA with 11 hits allowed and 27 strikeouts in 20 2/3 innings.

Opposite Freddy Peralta on a sweltering afternoon, Steele was in pitch-to-contact mode early on. He induced eight ground balls from the first 10 batters he faced, including an infield single to Escobar in the opening frame.

Steele did not record a strikeout until the fifth inning, when he sent a 1-2 curveball tailing low and out of the zone, and out of Kolten Wong's reach. That was the start of the third time through the order for Steele, who has two fastballs (four-seam and sinker), two breaking balls (slider and curve) and a changeup.

Steele said that his slider was a bit flat in the hot and humid conditions, so he had to adjust both in the moment.

“Going over the game plan prior to the game,” Steele said, “the sinker and the changeup were something that looked like it was going to play. So I threw more changeups than I usually do, more sinkers than I usually do. That was kind of part of the game plan.”

Earlier this season, when Steele filled a need in the Cubs' bullpen and posted a 2.03 ERA in 13 1/3 innings, he could narrow his arsenal at times. Now he will begin learning how to build a game plan for his full repertoire as he turns lineups over.

"He has the ability to spin two different breaking balls," Hottovy said. "He still has the changeup that he didn't even have to really break out. He's got five pitches. Five distinct pitches. It's really encouraging. We're just going to keep seeing him build.

"I'm really excited for the future for him and what he can do at this level."

And moments like the one in May against the Dodgers helped Steele know he can have success in the big leagues.

“Coming up in the bullpen first, it helped a ton,” Steele said. “I was able to get the first actual debut out of the way. It really helped me settle in as far as the mental side goes. I knew that I could pitch at this level. Everybody believed in me.”