PEORIA, Ariz. -- The Padres spent the offseason building one of the most complete bullpens in baseball, adding late-inning weapons from both sides. On the surface, they didn't leave much room for a spring surprise.

But what if that spring surprise is a prospect with a 99-mph two-seamer that moves? And what if he pairs that heater with a slider that bites? And, oh yeah, he's only been a pitcher for a year, so there's no telling what his ceiling might be?

Yeah, there's probably room for an arm like that.

Through three outings this spring, Javy Guerra has yet to allow a run. It's been a year since he began his transition from shortstop to the mound. His ascension has been nothing short of remarkable.

"I'm surprised sometimes at where I am right now," said Guerra. "But I feel good about it. I feel good on the mound, I feel good in the bullpen during the game. The more I pitch, I'm feeling more comfortable."

Guerra's undeniable talent is only part of the reason the Padres have pushed him so quickly. He spent his first six seasons in pro ball as a shortstop. That time in the Minors left Guerra out of options this season.

If the Padres want to send Guerra to the Minors, they first need to place him on waivers. The more he pitches, the more unlikely it is that Guerra would pass through waivers without being claimed by a rival.

So, yes, the Padres have a vested interest in Guerra's success this spring. But they aren’t handing him a roster spot.

"We've got a very talented group of guys competing for bullpen spots," said manager Jayce Tingler. "That's a factor. It's not just: 'He's out of options.' He's got to go out and earn this."

So far, Guerra is doing exactly that. He's increased the use of his sinker -- a pitch that averaged 98.8 mph last season. Catcher Austin Hedges says it's gained movement, too.

"This guy hasn't even pitched a year, and he took my thumb off with a pitch," said Hedges, who caught Guerra on Sunday. "That arm -- that's a very, very, very, elite arm. I don't know where in the league, but it's in the top something percent of just arms.

"You look at what he did at shortstop -- that athleticism, the 'whippiness' of his arm. ... I don't know if I've seen anything like it."

For years, Guerra ranked among the game's top shortstop prospects. He arrived in San Diego in the 2015 trade that sent Craig Kimbrel to Boston.

Guerra was an excellent defender at shortstop, with an obviously elite arm. But his bat never translated. In seven seasons in the Minors, he posted a .237/.290/.374 slash line, striking out at a 29 percent clip.

"I don't look back and think about anything," Guerra says. "I'm just here now, trying to get a job as a pitcher."

Guerra freely admits that pitching feels like a better fit. He says it's "more relaxing" -- as though standing on a mound with thousands of eyes trained on your every move qualifies as "relaxing."

For Guerra, maybe it really is. The Padres converted him last spring, and during his first bullpen session, he hit 100 mph. Better still, he threw strikes. In 21 Minors appearances last season, Guerra posted a 3.38 ERA with a 35 percent K-rate, before earning a September callup.

"He's been doing it a little bit over a year," Tingler said. "Are there going to be hiccups? Yeah. The upside to that is that he's only been doing it a year. There's going to be a lot of growth."

Tingler might need to find a spot for Guerra in his bullpen after all. José Castillo and Andres Muñoz have options, and both are on slower progressions this spring. It's possible one of them starts at Triple-A.

Right now, the upside to keeping Guerra is undeniable.

"He could be an elite big league reliever, 100 percent, no doubt in my mind," Hedges said. "No one is going to want to face that dude."