CHICAGO -- The first pitch of Caleb Kilian's career was much-anticipated. It arrived at 6:14 p.m. CT on Saturday night, popping into his catcher's glove for a called strike to Tommy Edman. Two pitches later, when Edman swung through an elevated fastball for a strikeout, the Wrigley Field crowd was buzzing.

After four more pitches, Kilian racked up a strikeout of Nolan Gorman. The rookie then shattered the bat of slugger Paul Goldschmidt, inducing a groundout. By this point, as Kilian walked off the field, a customary fist bump from manager David Ross awaiting him, it was easy for fans to start dreaming.

• Box scores: Game 1 | Game 2

"You try not to hype it up too much," Ross cautioned early Saturday morning. "I don't think any one player is ever like the savior, right?"

Maybe not, but Kilian arrives as possibly the most hyped pitching prospect for the Cubs in a decade, and perhaps even longer. And for three innings, the kid was perfect against the rival Cardinals at the Friendly Confines in a nationally televised doubleheader nightcap.

In the end, it was not a perfect outing for the 25-year-old Kilian, who took a no-decision in what ended as a 7-4 loss in 10 innings. But it was a tantalizing performance that followed a standout start from fellow Cubs rookie Matt Swarmer in a 6-1 win in Game 1. On this day, two potential pieces of Chicago's future were on display in promising fashion.

"This is a fun, exciting day," Cubs pitching coach Tommy Hottovy said.

The excitement surrounding Kilian's arrival is understandable.

Last summer, when the Cubs used the Trade Deadline to move pieces of their past core to reel in a pile of prospects, Kilian was a key acquisition in the deal that sent Kris Bryant to the Giants. Kilian was brilliant through High-A and Double-A last year and then kept his foot on the gas in the Arizona Fall League. In the AFL title game, he spun six perfect innings.

As injuries and other issues hit the Cubs' rotation this season -- and Kilian kept blowing hitters away with Triple-A Iowa (2.06 ERA in nine outings) -- it became increasingly clear that his promotion was imminent. He got the news  while celebrating his 25th birthday on Thursday.

“It was the best birthday present ever,” Kilian said. “It was the best day ever. The best day of my life. To be able to debut at Wrigley, Saturday night, against the Cardinals, and it starts raining, tie game in the ninth, I couldn't ask for anything better.”

In the hours before Saturday's first game, Kilian arrived and headed out to the dugout in street clothes to get his first look at Wrigley Field. He had never been to the old ballpark previously.

“It was breathtaking,” he said.

He then got to watch his former Triple-A rotation-mate carry a no-hitter into the fifth inning against St. Louis. Swarmer ended with a quality start, baffling the Cardinals with a fastball-slider mix en route to his first career win.

"It's incredible," said Swarmer, who was making his second career MLB start. "I just always thought about being here. Now, I'm competing with the best guys. It's so cool. I'm just living the moment right now."

Kilian looked poised in his moment in the spotlight, too.

The Cubs' No. 5-ranked prospect, per MLB Pipeline, needed just 31 pitches to breeze through the first three innings. He struck out four in that span, showing off a mix of sinkers, cutters, four-seamers and curves. That run included a strikeout of Yadier Molina, creating a roar of approval from the North Side crowd.

“Yadi, I watched him when I was a little kid,” said Kilian, who struck out the Cardinals catcher twice. “It's kind of crazy to face guys like that.”

Kilian reached as high as 97 mph with his fastball, but sat more in the 93-95 mph range, while producing soft contact (81.5 mph average exit velocity) when St. Louis did put the ball in play. The Cardinals broke through for three runs in the fourth -- two via a double by Brandon Donovan -- as the rookie momentarily fought his command.

Ross sent Kilian back out for the fifth and the right-hander responded with one more scoreless inning, ending it with a called third strike to Edman.

“The wheels didn't fall off,” Ross said. “You just get him back on that horse. He handled that really well.”

It was another standout Cubs rookie, Christopher Morel, who took Kilian off the hook for a loss with a game-tying RBI double in the sixth. Morel has a franchise-record 19-game on-base streak to begin his career, offering some more homegrown hope for a club trying to construct its "next great Cubs team," as president of baseball operations Jed Hoyer has repeated.

Kilian represents a critical part of that blueprint for a Cubs team that earned a reputation for a lack of internal pitching development. Arms like Justin Steele, Keegan Thompson and Adbert Alzolay started to buck that trend in recent years, followed by some more in-house arrivals this year like Scott Effross, Brandon Hughes, Ethan Roberts and Swarmer.

That list will keep growing.

"It speaks to what the Cubs have tried to do to develop pitching," Hughes said. "It's fun to see Cub-grown pitchers coming up through the system."

Kilian smiled when asked about all the hype surrounding his debut, and all the Cubs fans in attendance and tuning in to get their first look at the prospect.

“I just think people come out here to watch the Cubs,” Kilian said.