PEORIA, Ariz. — Padres reliever Yuki Mastui’s participation in the World Baseball Classic is in doubt after he experienced “tightness” in his groin on Thursday.

“We’ve got to see how he comes out of this day off and then how he feels tomorrow and then what his schedule looks like going forward,” Padres manager Craig Stammen said. “Obviously, I think it puts the WBC in question.”

While saying it would be left to Matsui to decide whether to play in the tournament that begins March 6, Stammen indicated the odds are against the left-hander being a part of Samurai Japan.

“He has got to make that decision,” Stammen said. “He has got to be able to talk with the coaches and the (general manager of Team Japan) and see if that’s still an option for him. It’s going to be a tough road for him to get healthy enough to be ready to pitch in the WBC. But I’ll let him address that. … We’ve had internal conversations about it. Ultimately, it’s up to him. We can’t call Team Japan and say, ‘Hey, Yuki is not pitching.’ Yuki has to make that decision, and I think he’ll come to a pretty good decision on that.”

Matsui’s live batting practice session was cut short Thursday after about 20 pitches. He appeared to be walking without much noticeable impediment Friday morning, and Stammen said Matsui could play catch as soon as Saturday.

However, his scheduled appearance in Sunday’s game against the Dodgers has been scratched. He was scheduled to pitch at least one more time before leaving for Japan next weekend.

Adam’s progress

Jason Adam fielded grounders earlier this week, but only while remaining stationary. He recently began change-of-direction drills. On Thursday, physical therapist Scott Hacker and strength and conditioning coach Jay Young introduced “mild reactive” components to Adam’s running program to simulate game situations.

That sort of agility work will likely continue for a couple of weeks. If all goes well, Adam can then work his way into a full fielding practice before pitching in backfield games and then appearing in Cactus League games.

The final stages of his recovery from September’s quad rupture might seem like plodding progress, but Adam remains on track to potentially be ready for the start of the season.

“I think they’re on board,” Adam said of the medical staff. “They haven’t told me ‘no’ yet.”

Adam has been throwing bullpens since early December and has said he is further along in his throwing program and feels better pitching than he did last year at this time.

“Pitching-wise, we’re … on pace, beyond on pace,” he said. “It’s just a matter of being cleared. So once that happens, it’s, ‘Let’s roll.’”

Adam, whose 1.66 ERA over 92 innings is best in MLB among qualifying relievers since he made his Padres debut on July 31, 2024, weill wear a small brace on his left leg while pitching this season.

“Nothing too cumbersome,” he said. “Just something to give everyone a little peace of mind, I think. And me. I feel confident with or without, but it doesn’t hurt to have a little extra support.”

Song soon

The Padres’ first lineup of the spring featured five everyday players, two projected regulars and another guy with a legitimate shot to be on the big-league roster on opening day.

Craig Stammen’s first Padres lineup. 👀
via @Padres pic.twitter.com/LTE9BjrpNZ

— Kevin Acee (@sdutKevinAcee) February 20, 2026

One player virtually assured of playing a fair amount this season who didn’t make his Cactus League debut on Friday was Sung-Mun Song.

Song was never going to play this early after suffering an oblique injury while taking batting practice in January. But his progress has been great enough that he is expected to play in the coming days.

The 29-year-old Korean import, who signed a four-year, $15 million contract in December, took his first live batting practice on Thursday.

“I’m fully recovered with my injuries,” Song said Friday morning through interpreter Sam Jeong. “… My body feels great, so I’m just waiting for a green light to play in a game.”

Song figures to get plenty of work once shortstop Xander Bogaerts and third baseman Manny Machado depart for the WBC on Sunday.

Song primarily played third base in the KBO, but the Padres plan to try him at shortstop, second base and left field.

Fermin’s Waldron adventure

Freddy Fermin caught a knuckleballer for the first time Thursday when he was the catcher for Matt Waldron’s bullpen session.

“It’s really nice,” Fermin said of Waldron’s signature pitch. “It’s moving. You have to try to catch, not frame that pitch. Just catch. It’s hard to catch that thing. … It was fun. It was crazy.”

While Luis Campusano has used a special knuckleball glove when catching Waldron, Fermin wore his regular catcher’s glove. Stammen said both catchers will get work with Waldron this spring, and they will determine who his catcher will be if he makes the roster out of camp.