LOWELL — Pitchers are measured by all types of numbers by Major League Baseball scouts.

When it came to gauging Durbin Feltman’s long-range potential as a prospect, the digits that enabled him to be selected high in this year’s June draft ranged from 96 to 99 mph.

That’s the speed Feltman’s fastball routinely travels to home plate. And the arithmetic added up to the hard-throwing closer from Texas Christian University being selected in the third round, 100th overall, by the Boston Red Sox in the MLB Draft.

“I haven’t touched 100 yet,” said Feltman, 21, a native of Conroe, Texas who is now pitching for the Lowell Spinners. “I’m working on triple digits.”

Feltman was a force at the back end of TCU’s bullpen the past three seasons. He was a first-team All-Big 12 selection this spring, finishing with six saves, a 0.74 ERA and 43 strikeouts in 24 innings. He ended his college career tied for the most saves in TCU’s storied history with 32.

“I like being a reliever because it’s the closest you can get to being an every day player,” said Feltman. “I never started at TCU. I was always the late-inning guy. I love the role.

“You get to play close to every day. Being as competitive as I am, I don’t think I could sit there four days until the next start, especially after a bad outing. Get me back out there and let me go again. I love being out there with the game on the line and all the chaos that comes with it.”

Feltman, a right-hander who stands 6-feet and weighs 205 pounds, was a catcher throughout high school. As a senior in high school, Feltman was a starting pitcher whose heater topped out in the high-80s, and caught when he wasn’t on the mound. He was recruited to TCU as a two-way player. After the TCU staff realized he possessed a fastball that traveled the same speed as the average July temperature in Fort Worth, Feltman’s days as a catcher quickly came to an end.

“They taught me how to pitch (at TCU),” said Feltman. “I stopped throwing like a catcher, from my ear. I was all arm and no legs. Then all of a sudden I was using my legs and my velo started jumping up.”

His velocity didn’t just jump up, it soared. In the fall of his freshman season, he was occasionally hitting the low-90s on the gun. By the following spring, Feltman was throwing over 95 on a regular basis.

“I tell everybody if I knew (how I increased my velocity so fast), I’d make a lot of money off that throwing program,” said Feltman. “Really, it was just within five months that my velocity went from 90, 91 to clicking all the way to 98.”

Feltman’s electric stuff, which includes a nasty slider, was on display during his pro debut against the Aberdeen IronBirds on Friday. He threw a scoreless inning, notching two strikeouts.

“He looked really good,” said Spinners manager Corey Wimberly. “He threw the ball well. The ball came out good. We heard the hype, and he definitely didn’t disappoint.”

Feltman only pitched 88.1 innings at TCU so his arm is relatively fresh compared to many pitchers entering pro ball.

“I’ll tell you what, to have someone who hasn’t had that much wear and tear on his arm is definitely a plus for him,” said Spinners’ pitching coach Nick Green. “If you had told me this guy hasn’t pitched that long and he was a catcher, I would have thought you were lying.”

His ability to listen and learn has helped Feltman make a smooth transition to pro baseball.

“He’s been a sponge,” said Green. “He’s been soaking everything he can learn in. He’s been all ears. Some guys of his stature, being a high-round pick, come in with a big ego. But he’s been great. He works hard. He does his throwing program. It’s great to have him.”

How long Feltman continues to pitch at LeLacheur Park remains to be seen. There have been reports that he may accelerate through the Red Sox farm system — and could even join Boston’s bullpen before the end of this season.

Since 2010, the only two pitchers chosen in the first three rounds of the amateur draft who pitched in the majors the same year they were drafted are Chris Sale (2010, first round, Chicago White Sox) and former TCU star Brandon Finnegan (first round, Kansas City Royals, 2014).

“Everybody has different expectations,” said Feltman. “I feel like mine are higher than anybody’s. I would love to do what (Finnegan) did. That’s my dream. That’s my goal. I’m working on it. If it doesn’t happen, if I’m not ready, then I’m not ready. But I’d definitely like to try.”