Fernando Romero threw a fastball on his 97th pitch, the final one of his Major League Baseball debut. The pitch was called a ball, resulting in a walk, but it registered 96 miles per hour on the radar gun at Target Field.

Romero looked like he was just getting loose.

“When the opposing team is making comments mid-at-bat about the stuff,” Twins catcher Jason Castro said, “that’s a pretty good indicator that you’ve got pretty good stuff.”

Romero showed why his stuff gives the Twins organization hope he can become a top-of-the-rotation flamethrower. The 23-year-old threw 5⅔ scoreless innings to earn his first career victory and brighten the mood inside the Twins clubhouse with a 4-0 victory over the Toronto Blue Jays on Wednesday.

A big-league debut in the midst of a team’s tailspin isn’t the most ideal circumstance for a starter. This has been a miserable stretch for the Twins. They desperately needed a positive outing from Romero, who described his debut as a “big opportunity in my career and my life, too.”

“I’ve been feeling no pressure,” he said.

He didn’t look or pitch nervous. His performance wasn’t necessarily smooth sailing, but his velocity and movement on pitches showed why MLB.com ranks him as the No. 2 prospect in the Twins system and the No. 66 overall prospect in baseball.

Romero’s fastball hit 98 miles per hour. His slider broke sharply and registered between 88-91 mph. Castro said the scoreboard mistakenly credited Romero’s changeup as a fastball a few times because he also threw it in around 90, the result of him being “amped up.”

“If we can get him to throttle off a hair more is probably where we want to be,” Castro said.

Romero gave up four hits, walked three and hit one batter. He allowed two baserunners in three of his five innings. He had difficulty locating his pitches at times, probably partly because of nerves and excitement.

He never looked rattled though. He got out of jams by making effective pitches when he needed them. That’s the luxury of having a pitcher who can blow away hitters with a 98-miles-per-hour fastball.

“If I had that [repertoire],” manager Paul Molitor said, “I’d trust it a little bit, too.”

This is new ground for an organization that has traditionally featured a starting rotation known more for control than fastball dominance. Romero wants to attack hitters and challenge them to hit his upper-90s fastball or his nasty slider.

“He’s got so much movement and velocity on his pitches that pretty much regardless of whatever pitch he decides to go with, he’s got a pretty big margin for error,” Castro said.

Romero started the season in Class AAA Rochester after a fantastic spring training in which he did not allow a hit in eight innings. The organization probably didn’t expect to promote him this soon, but a lousy few weeks has created a sense of urgency.

The team could no longer afford to sit patiently and hope Phil Hughes started to pitch better. Too much is at stake to keep spinning their wheels. The hope now is that Romero settles in and remains part of the rotation for a long time.

“I’m thankful the Minnesota Twins gave me the opportunity,” he said. “I don’t have time to waste it.”

Romero, a native of the Dominican Republic, called his mother after being told he was headed for the big leagues. She shouted and jumped up and down, then passed along the news to his father.

“My dad went crazy,” he said.

The reaction probably was similar while watching his debut. Molitor removed Romero with two outs in the sixth inning. Romero pointed to the sky as he walked off the field to a standing ovation.

After the game, Molitor presented him with a game ball that was placed inside a baggie. Written on the bag was “first strikeout” in black marker. Romero struck out the first batter he faced, Curtis Granderson.

“That’s what I call history,” Romero said.