Joe Girardi took notice of lefthander Jordan Montgomery early on, well before the Grapefruit League season began.

“Probably when I saw him throw his bullpens,” Girardi said late in the spring. “I just thought, ‘This is a different look. We haven’t seen this a lot.’ It’s not a fastball that’s 100 [mph], so there’s obviously some deception there. We became really curious.”

Still, Montgomery, who will make his big-league debut Wednesday afternoon against the Rays, did not begin the spring as one of the names mentioned in the fifth-starter competition.

The 24-year-old was, as general manager Brian Cashman said Tuesday, a “dark horse,” though on the organization’s radar more than it was letting on publicly.

And when none of the quintet competing for the two open rotation jobs — Luis Severino, Chad Green, Luis Cessa, Bryan Mitchell and Adam Warren — went out and staked an outright claim to a job with a standout performance, a door opened for Montgomery during the last two weeks of the spring.

He took advantage, striking out eight in 4 1⁄3 innings in his first spring start, March 23 against the Rays in Port Charlotte, and following that up six days later in Dunedin against the Blue Jays, allowing one run, six hits and a walk in five innings. That outing impressed Cashman because Montgomery — a finesse pitcher who features a fastball, slider, curveball and changeup mix — “didn’t have his best stuff” but produced nonetheless.

advertisement | advertise on newsday

“He’s won the first leg of the race and the race will continue,” Cashman said. “Young players’ performances are volatile. He could be here a long time, or make us adjust. If he pitches the way he did in the spring, we’ll be very happy.”

The Yankees drafted Montgomery in the fourth round of the 2014 draft of the University of South Carolina and looked at the 6-6 pitcher as having the potential to be a fast-riser through the system. “Just one of those guys that when you watched him, he had deception to his stuff, he was able to pitch and had kind of a unique plane to his fastball that was tough on hitters,” Damon Oppenheimer, the Yankees amateur scouting director, said by phone Tuesday.

Amateur scout Adam Czajkowski, who is no longer with the club, saw Montgomery the most, and pitching analyst Scott Lovekamp and cross-checker Brian Barber watched a fair share of the lefty’s outings as well, Oppenheimer said.

The talent evaluators’ reports were consistent.

“It was always the hitters didn’t have a comfortable at-bat, they didn’t square the ball up,” Oppenheimer said, adding hitters seemed to have difficulty seeing the ball well out of Montgomery’s hand. “He didn’t give up a lot of hard contact. It made you think the stuff was playing a little more firm than the gun would tell you.”

Yankees videos

Montgomery went 14-5 with a 2.13 ERA in 25 starts in Double-A and Triple-A last season, including 5-1, 0.97 after his promotion to Scranton/Wilkes-Barre. One opposing team scout said Tuesday Montgomery pitched effectively at those levels the same way he did in college.

“Fastball was 88-92, slider 81-84, curveball 75-79, changeup 80-82,” the scout said. “Four-pitch guy who has feel and command capabilities. He’s sneaky, ball gets on hitters quick, and he can mix speeds. Stylish yet deceptive.”

It is, of course, just one start. Merit got Montgomery to the majors sooner than expected, the hard part is sticking.

“Remains to be seen,” Cashman said. “But he earned the right to take first shot.”