GOODYEAR, Ariz. -- It appears that Reds ace Luis Castillo will not be able to take the ball to pitch on Opening Day and possibly not during the first time through the rotation because of a right shoulder issue.

“I felt a little bit of soreness in my shoulder once we got into training and when I got here,” Castillo said via translator Jorge Merlos. “We’re just working on it to get it better and to be ready for the rest of the season.”

Castillo arrived at camp on March 14, a couple of days after most of the team, because of travel issues leaving the Dominican Republic.

“He’s actually throwing distance today, like throwing long toss, so he’s fine,” Reds manager David Bell said. “He got here late and then he had a little bit of a sore shoulder -- that skipped a day or two. We’re still trying to build him back into a bullpen [session]. He is obviously a little bit delayed.”

Castillo has been throwing long toss at distances of 60-75 feet.

“And we’ve been feeling pretty good when doing those workouts,” he said.

There is no timetable when Castillo could be ready. The right-hander has no injury history and has never missed a start previously in the big leagues.

“I’ve never even had to do rehab of any sort. I’ve never had to do that,” Castillo said. “God has a plan, and we’ll fight through it.”

Bell didn’t fully rule out Castillo from pitching early in April, noting he could be ready to throw two or three innings. That wouldn’t be so unusual this year because of a shortened Spring Training due to the lockout.

“He’s like, ‘I feel great,’” Bell said. “We’re just playing it slow with him. After he throws long today, then we can get him back on the mound. If that changes, I’ll let you know. We feel good about where he is.

“I’m still optimistic, but most likely he’s probably out for Opening Day, or maybe even the first time around.”

Castillo, 29, was 8-16 with a 3.98 ERA with 192 strikeouts in 33 starts and 187 2/3 innings last season. In his first 11 starts, he was 1-8 with a 7.22 ERA before posting a 2.73 ERA over his final 22 outings.

Cincinnati named Castillo as its Opening Day starter in 2019 and ’21.

“Opening Day is such a special day, especially for pitchers to go out as a starter,” Castillo said. “But you don’t want to put too much on your arm and make your arm overdone by the time you get to Opening Day. We just have to give the arm it’s time, and it’ll let us know when it’s ready.”

Who will start Opening Day?

“I will tell you that [Wednesday],” Bell replied.

However, it lines up for Tyler Mahle to make his first career Opening Day start on April 7 at Atlanta.

Mahle’s next Cactus League start is on Wednesday vs. the Brewers.

What does this mean for the rotation?

That could mean two open spots for the first turn in the rotation instead of one.

Bell also revealed that left-handed starter Mike Minor -- acquired last Wednesday from the Royals -- also had some soreness.

“After his live BP, he had a little bit of [left] shoulder soreness, which is very normal and common for him,” Bell said. “He is throwing a bullpen today, so he should be back on track.”

Bell believed it was realistic for Minor to pitch the first time around in the rotation.

Besides Mahle and Minor, Vladimir Gutierrez is the only other starter locked into a rotation spot.

The competition for the vacancies most likely includes Top 10 prospects Hunter Greene (No. 1), Nick Lodolo (No. 2) and Graham Ashcraft (No. 8), along with Tony Santillan and left-hander Reiver Sanmartin. Both Santillan and Sanmartin have chances at making either the rotation or bullpen.

Lodolo and Ashcraft are the most stretched-out pitchers after both were part of the club’s early Minor League camp that started last month. However, Lodolo only has three starts as high as Triple-A on his resume, and Ashcraft has not pitched above Double-A.