Domingo German of the Yankees pitches in the second inning...

Domingo German of the Yankees pitches in the second inning against the Astros at Minute Maid Park on May 1, 2018 in Houston,. Credit: Getty Images / Bob Levey

HOUSTON — Domingo German threw well in the spring, impressing the Yankees with his calm demeanor and pitch repertoire, including a curveball Dellin Betances calls “really filthy.”

But the righthander, who posted a 2.30 ERA and struck out 17 in 15 2/3 innings, was left off the 25-man roster when camp broke at the end of March because there were no open spots on the staff.

The 25-year-old German, acquired as part of the Nathan Eovaldi deal with the Marlins in December 2014, said he wasted no energy being disappointed.

“I didn’t make the team out of spring but I knew I was a phone call away and therefore I needed to be ready,” German said Wednesday through his translator. “I couldn’t lose focus on my training and my work because I knew an opportunity was going to come eventually.”

It has come.

First on April 7, when CC Sabathia was placed on the disabled list with a right hip strain and German was recalled from Triple-A Scranton/Wilkes-Barre.

An even greater opportunity came Tuesday night when German suddenly was thrust into the game against the powerful Astros when Jordan Montgomery left after one inning with what was diagnosed Wednesday as a left flexor tendon strain.

German matched the brilliant Justin Verlander zero for zero over the next four innings, striking out four.

Aaron Boone said Montgomery will be out 6-8 weeks and his rotation spot belongs to German, who will get his first shot at keeping it Sunday at the Stadium against the Indians. It will be his first career start.

“It was an unexpected and unfortunate opportunity to pitch and come in and face the world champs,” said German, who has been mentored by close friend Luis Severino. “To be able to do your job, it’s exciting.”

Neither excitement, nor nerves showed Tuesday. That was the case whether German struck out a batter or allowed a hit. In either instance, his facial expression rarely changed.

“That’s part of my personality, especially in tough moments,” said German, who missed the entire 2015 season recovering from Tommy John surgery. “A tough situation in a game, I want to be as calm as possible. At the same time being aware what’s going on around me but you have to focus on what you’re doing, focus on your job and what you’re trying to accomplish. For me it’s just executing one pitch after another. Finding a moment where I see myself executing my pitches.”

Pitches that have left an impression.

“You see the stuff he has, he has electric stuff,” Betances said. “Sinker is pretty filthy, a really filthy breaking ball and a great changeup as well, so he has three plus-pitches he can get outs with it. Obviously he knows this is a big opportunity for him and he’s trying to take advantage of it. He’s confident with the stuff he has and he’s just been trying to stay ready.”

German, who has a 3.77 ERA in five appearances and has struck out 18 in 14 1/3 innings, said his solid spring helped his confidence but didn’t instill him with it. That existed already.

“I was lucky enough to have a good spring and that definitely gave me a boost in confidence,” German said. “But I can tell you that even before I got to spring training, in my mind, I had something to provide. I felt I could help in whatever way [I was needed].”

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