SAN FRANCISCO -- Last season, Javy Guerra -- a light-hitting, defense-first shortstop -- earned his first Major League callup.

On Sunday, the Padres promoted Guerra once again, as one of three September callups. This time he’s a hard-throwing right-handed reliever.

Guerra’s story is nothing short of remarkable. When the Padres acquired him from Boston in the Craig Kimbrel deal four years ago, he was a highly touted shortstop prospect. But his bat lagged well behind his elite defense, and before this season the Padres asked him to attempt a conversion to the mound.

"I just told myself I'm going to do it," Guerra said. "I went step by step, and now I'm here."

Right-hander David Bednar and outfielder Travis Jankowski were also promoted Sunday. To clear space for Bednar on the 40-man roster, righty reliever Robert Stock was moved to the 60-day injured list. He will miss the remainder of the season with a right biceps strain.

With Guerra, the Padres knew they were on to something right away. In his first bullpen session at the Peoria Sports Complex, he reportedly threw 100 mph -- and he threw strikes.

Now, Guerra sits in the mid-to-high 90s with a slider that bites. He posted a 3.38 ERA in 21 appearances in the Minors this season.

"It was something we had deliberated on for a long time," Padres manager Andy Green said of Guerra's switch to the mound. "... That first bullpen was like, 'Well, this is a no-brainer.’"

Bednar, meanwhile, will also be making his big league pitching debut when he takes the mound for the first time. He posted a 2.95 ERA at Double-A Amarillo with 86 strikeouts in 58 innings.

Bednar's callup is a sign that he factors prominently into the club's long-term bullpen plans. A 35th-round Draft pick out of Lafayette College, Bednar is the highest Padres Draft pick to reach the big leagues under general manager A.J. Preller.

On callup day, here's a look at the ways in which the Padres farm system is making an impact:

Arrival: Fernando Tatis Jr.

Among the Padres' preseason Top 30 prospects, 11 of them spent time in the big leagues this season. Chris Paddack and Francisco Mejia broke out when handed regular opportunity. But no one made as big an impact as Tatis. Before he went down with a back injury in mid-August, Tatis was on his way to one of the best rookie seasons in Padres history. He was batting .317/.379/.590 while showcasing a dazzling brand of defense and baserunning.

Breakout: Luis Campusano

The Padres like the production they've gotten behind the plate this season with Mejia and Austin Hedges in something of a 60/40 split. Mejia brings an excellent bat for the position, and Hedges brings elite defense. Campusano, meanwhile, has the potential for both. At Class A Advanced Lake Elsinore this season, Campusano batted .325/.396/.512 with 15 homers while anchoring the starting catcher role.

Something to prove: Taylor Trammell

The Padres landed Trammell in the trade that sent beloved slugger Franmil Reyes to Cleveland. That decision wasn't easy, but the Padres like the upside Trammell offers as a potential center fielder and all-around athlete. But Trammell has taken a step back in 2019. He's hitting .230/.336/.333 at Double-A this season, including a .214/.296/.321 mark since he was traded to the Padres. Of course, part of the reason Trammell -- MLB Pipeline's No. 27 overall prospect -- was available in the first place is because he was struggling. He was an obvious buy-low candidate. But he needs a bounceback season in a big way in 2020.

Name to watch: Owen Miller

Luis Urias remains the favorite to anchor the long-term second-base job in San Diego. But his bat hasn't yet translated in the big leagues. As a result, the Padres view second base as something of an open competition entering 2020. That's where Miller comes in. A 2018 third-round pick, Miller has hit at every level, including a .289/.355/.425 line after his quick rise to Double-A Amarillo this season. He's a long shot for an Opening Day roster spot. But Miller, the team's No. 10 prospect, will almost certainly get his chance to make an impact in big league camp next spring.