PEORIA, Ariz. -- This was only the first step back for Sam Carlson, but clearly from the broad smiles and heartfelt hugs, it was a big one for the promising Mariners pitching prospect.

The 21-year-old right-hander threw 20 pitches in a live batting practice session against fellow Minor League prospects on a backfield at the Mariners’ Peoria Sports Complex on Friday, his first time facing hitters in 32 months after a grueling recovery process from Tommy John elbow surgery and several setbacks.

“I’ve been at points in the game where I’ve literally hated it, and I’ve thought, 'Am I ever going to throw again?'” Carlson said. “I’ve had days where I’ve cried myself to sleep. It’s been a lot. It really tested my character.”

Carlson has pitched just three innings of Arizona League Rookie-level ball since he was selected by Seattle in the second round of the 2017 Draft out of Burnsville High School in Minnesota. But the 6-foot-4, 195-pounder has such upside that he’s still ranked as Seattle’s No. 12 prospect by MLB Pipeline and regarded by the Mariners as part of their future wave of pitching talent.

The Mariners will proceed cautiously with Carlson and see where things go this spring before assigning him to one of their Minor League affiliates. He’s not in Major League camp, but instead part of their Minor League mini camp that is already underway.

But just seeing him throw off a mound was a welcome sight and no one was happier than Carlson.

“I was nervous, man,” Carlson said. “It was weird. I was kind of like, ‘What’s going on right now?’ But it was cool. This is what I love doing. It was awesome. I’m just excited to get to work because I’ve been dying to do this since I was 18. I had to put it on hold, but now I’m back at it.”

Carlson said that his low point came last August when he thought he’d torn his ulnar collateral ligament again during a bullpen session. It turned out to just be an impingement in his surgically-repaired elbow that cleared up with more rest, and he’s been throwing well since taking some time off.

Some pitchers come back from Tommy John and are able to throw as hard or harder than prior to the surgery, but Carlson isn’t worried about that.

“I just am doing what I can to be the best player I can,” he said. “I have no scale. I have no standard. I’m just doing everything I can that I know I can do to perform at the highest level and fulfill my dream one day.”

During his down time, Carlson took college courses and is now a junior at Arizona State, pursuing a degree in Business Administration. But his first order of business is to get prepared to throw in games, something he hasn’t really done since his high school days.

As good as it felt to throw in a controlled situation against teammates on Friday, can he imagine what it will feel like to take the mound sometime soon in a game?

“I can’t,” he said with a smile. “But I’m stoked. I mean, honestly it’s been so long. But even just seeing a hitter in the box, it brought back so many memories. I’m really happy right now.”