PEORIA, Ariz. -- "Remember this injury?" José Castillo says, pointing to a finger on his left hand.

Indeed, amid the spate of ailments that have kept the Padres left-hander off the field over the past three seasons, it can sometimes seem hard to keep track. Castillo missed the final two months of the 2019 season due to issues with a tendon in his left middle finger and hand.

"For me, that was the worst injury," he said. "It's like my world came crashing down that day."

It's the last time Castillo took the mound in a Major League Baseball game. He had battled his way back from early-season elbow trouble that year to pitch two-thirds of an inning against the Rockies in mid-August. He struck out Nolan Arenado and Daniel Murphy. And then, as quickly as Castillo's season began, it was over.

Then came a 2020 season which never got off the ground as Castillo dealt with back trouble. In '21, he was shut down early in camp and underwent Tommy John surgery in March.

Amid the uncertainty, the Padres designated Castillo for assignment last November. But they were thrilled when he opted to return on a Minor League deal, knowing he could be a dominant left-handed weapon out of their 'pen when healthy.

For Castillo, that feeling is mutual. He never wanted to go anywhere else.

"I feel like I have a debt to pay to San Diego," Castillo said. "... They gave me the opportunity. I need to repay that."

Thus far, Castillo's recovery from Tommy John surgery has been a smooth one. He's thrown 10 bullpen sessions, and is hopeful he'll get to face live hitters at some point later this month. In April, he might see Minor League game action.

The Padres, of course, aren't going to rush things with Castillo. The first eight of his bullpen sessions featured exclusively fastballs. It wasn't until recently that he began snapping off his trademark slider -- the pitch against which opposing hitters batted just .123 in 2018 with a 41 percent whiff rate.

"After almost three years, it feels amazing," Castillo said. "It's an amazing feeling to feel the arm with no pain, no discomfort, or nothing."

Castillo burst onto the scene with a remarkable rookie season in 2018. He posted a 3.29 ERA with a 2.64 FIP, while striking out 52 hitters in just 38 1/3 innings.

Some in the organization wondered, at the time, whether he might be future closer material. Then came the injuries. The Padres, with a bullpen logjam, removed Castillo from their 40-man roster ahead of the deadline to protect players from the Rule 5 Draft. Then, they secured his services on a Minor League deal.

"We're excited to bring José back," Padres general manager A.J. Preller said earlier this offseason. "Everybody that's seen him knows what his ability is when he's healthy. That's just the biggest key."

And Castillo knows it.

"I'm a super competitive guy, so for me, I want to be out there competing," Castillo said. "I wanted to contribute. I wanted to help. Unfortunately, my arm wouldn't let me. So I just want to get back to being healthy, helping the team out as much as I can."

If Castillo's rehab continues on a smooth trajectory, he might not remain off the 40-man roster for very long. He's confident the Padres will get the same strikeout artist who helped anchor the middle innings for them in 2018.

Well, not quite the same, Castillo says.

"Better," he clarified.

Minor League camp notes

• Though many Padres prospects have been in Peoria, Ariz., for several weeks, Sunday marked the official start of Minor League camp, and Monday was the first day open to the media. The full roster is comprised of nearly 180 players, who worked out on back fields 3-6. Players on the 40-man roster were not in attendance as Major League camp remains on hold during the lockout.

• Drills were limited on Monday. A handful of pitchers threw bullpen sessions, and the others went through pitchers' fielding practice. Position players worked on team defense before a series of fast-paced simulated games using high-velocity machines, rather than live arms.

• A standout from those Monday sim games: Esteury Ruiz. The 23-year-old utility prospect homered in his first two at-bats -- the first a booming shot to left field, and the second an inside-the-parker that center fielder Robert Hassell lost in the sun at the warning track. Ruiz hustled around the bases and scored with an acrobatic slide into home.