Kervin Castro can pinpoint the exact day his pitching career officially began: Dec. 24, 2014.

At 15, Castro viewed himself primarily as a catcher, but at the suggestion of his coaches in Venezuela, he decided to give pitching a shot. He hit 86 mph in his first bullpen session and 88 mph a week later, convincing his trainers that his future lay on the mound.

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Seven years later, Castro is in the midst of his first big league camp with the Giants and drawing high praise from manager Gabe Kapler, who has said he believes the 22-year-old right-hander has the potential to develop into a bullpen option for the club this season.

"That is a future Major League pitcher," Kapler said after Castro posted a quick, 1-2-3 inning against the Padres on March 5. "That pace, that tempo, he's on the mound and ready to deliver the baseball before the hitter is ready. He's pounding the strike zone, and when he's not in the strike zone he's very close to it and throwing his secondary weapons for strikes.

“He's just a really impressive kid."

It’s been a remarkable rise for Castro, who was added to the Giants’ 40-man roster along with fellow pitching prospects Camilo Doval and Gregory Santos in November. Castro admits that the move caught him a bit by surprise, as he hadn’t pitched above Class A Salem-Keizer and had only 89 2/3 professional innings under his belt after missing nearly three full seasons due to 2017 Tommy John surgery and the coronavirus pandemic last summer.

“I was the player with the least experience and the one that had thrown the fewest innings,” Castro said in Spanish. “But you saw the work that I put in and how prepared I was when I showed up for instructional league. It was something that I was hoping for, but I wasn’t sure it was going to happen. Thank God it happened, and I’m continuing to take advantage of the opportunity.”

Castro, who signed with the Giants for $100,000 in July 2015, has long been viewed as a sleeper prospect within the organization, but he opened eyes during fall instructs, when he touched 97 mph with his fastball and flashed a power curveball. He debuted on MLB Pipeline’s list of Top 30 Giants prospects earlier this month, coming in at No. 25.

“He was always a guy that very much intrigued us,” director of player development Kyle Haines said. “We felt like probably people weren’t giving him the credit that he deserved. I know internally our player development staff has always been high on him and always enjoyed working with him. We believed that people were a little light on him and that he was a little under the radar with us.”

That Castro managed to take such a meaningful step forward in his development amid the disruptions caused by the pandemic is a testament to his work ethic and dedication to his craft.

When Spring Training shut down last March, Castro found himself in a tricky spot, as he couldn’t return home to Venezuela, which halted all international travel in an effort to slow the spread of the coronavirus. Castro decided to head to Orlando, Fla., where he stayed with the family of José Salas, his longtime trainer in Venezuela. Salas’ eldest son, José Salas Jr., is a shortstop prospect for the Marlins, giving Castro a workout partner to quarantine with.

“They opened the doors to their home to me, and thankfully, I had the opportunity to live with them during the pandemic,” Castro said. “I feel really lucky that I had that opportunity when there wasn’t any baseball.”

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For the first month, Castro was largely restricted to the apartment and continued to work out with the limited equipment they had. Afterward, he was able to train alongside the younger Salas and his trainer at a nearby field, throwing bullpen sessions and facing hitters a couple of times a week to keep his arm in shape.

Castro also worked on improving his curveball. As a converted catcher, Castro was behind other pitchers in developing a feel for his breaking ball, a process that was further slowed by his rehab from Tommy John surgery. Still, the shutdown period gave him the perfect window to refine that pitch, which he fully took advantage of.

“The breaking ball was the area that we really wanted him to focus on,” Haines said. “He did everything that we had asked him to do back at Spring Training. He had worked on his own on it. We were really happy not only to see him work really hard and be in shape [at instructs], but he also worked hard on his weaknesses, so to speak, while still maintaining and even enhancing his strengths.”

Those strengths include some of the best control in the Giants’ system and an ability to work quickly on the mound. Castro has allowed four runs over 5 1/3 innings in six Cactus League appearances, but what has stood out the most has been his speedy pace, which has become a rare quality among Major League pitchers.

“I think a lot of times the pitcher’s ability to work quickly is just a byproduct of their confidence,” Haines said. “Sometimes I think the pitchers who end up working slower are just second-guessing themselves. They need more time to talk themselves into throwing the next pitch, whereas Kervin, he believes in himself. I think the other thing is being a former position player, he knows how much his defense really appreciates a pitcher that doesn’t put them to sleep.”

Castro has distinguished himself not only with his performance on the mound, but also with his off-the-field character. After being on the receiving end of the Salas family’s generosity last summer, Castro chose to pay it forward when heavy rainfall caused devastating flooding in a neighborhood in his hometown of Maracay in July. He texted his Giants teammates to help raise money to buy food, toiletries and other basic supplies to people who lost their homes in the floods and sent the funds to his wife and mom, who were able to distribute the aid in Venezuela.

“With the help of my teammates and coaches, we were able to raise money to bring food and other things to people who lost everything,” Castro said. “I’m very grateful to all my teammates who were able to help those people.”

The Giants have not yet announced where Castro will open the 2021 season, but it wouldn’t be a surprise to see him pitching in San Francisco at some point this year.

“It’s something I’ve dreamed about since I was a kid,” Castro said. “I’m going to keep working hard and keep developing so that when I get that opportunity, I can show the best of me and stay in the big leagues for a long time.”