What’s ailing Mookie Betts remains a mystery — his inexplicable stomach illness has left him at a loss for words.

Down from 175 to 157 pounds, the usually joyful and cheerful Betts had a sullen look on his sunken face as he tried to figure out what is causing his illness, which led to the Dodgers scratching him from the lineup ahead of Sunday’s Freeway Series exhibition opener against the Angels.

“I just want to play,” Betts said softly by his locker. “I’m tired of sitting, tired of just throwing up, tired of doing all this. I just really want to play.”

Betts was penciled in to start at shortstop, arriving at the ballpark with his symptoms subsiding. But just a few hours before the first pitch, he was scratched after unexpectedly throwing up again.

“My body’s just kind of eating itself,” he said. “It’s hard to not fuel it. And so every time — literally, every time — I fuel my body, I throw up… I don’t know what to do.”

He says his body feels great — he can work out and do almost everything as usual except eat. Betts has struggled to keep down solid food, the ordeal leaving him “scared to eat.”

“This is so touchy, man,” Betts said. “You think you feel good, and then you don’t really know. … Every time I eat something, it just comes right out.”

Betts said he never had a previous history of stomach issues. His vitals and blood tests have come back clean, but his stomach remains aggravated. Team doctors have put him on a new medication to calm his stomach, though he didn’t disclose what he’s taking.

His symptoms began two days before the Tokyo Series. He thought he would feel better after he arrived in Japan, but his symptoms worsened.

Whether Betts will be in the lineup for Thursday’s home opener against the Detroit Tigers is uncertain. Over the next few days, he will undergo more tests.

Although he’s eager to overcome his stomach troubles and take the field, Betts doesn’t want to put the Dodgers at a disadvantage. He believes that returning too soon could hinder the team’s performance and potentially put his health at greater risk.

“You’re already playing uphill,” Betts said. “I weigh 157 pounds, and that’s way underweight. … I’m not saying I don’t want to do it. Sure, if that’s what it takes, but does it logically make sense? And that’s the question we really need to answer.”

Blake Snell will start home opener

Dodgers starting pitcher Blake Snell, left, speaks with catcher Will Smith during an exhibition game against the Hanshin Tigers in Tokyo on March 16.

(Robert Gauthier / Los Angeles Times)

Blake Snell, who signed a five-year, $182-million deal with the Dodgers in the offseason, will make his Dodgers regular-season debut against the Detroit Tigers on Thursday.

“He was certainly honored, excited,” Roberts said. “Blake chose to be a Dodger for various reasons. And for him to start the home opener here at Dodger Stadium, I think it’s just something else he can add to his already great career.”

It will be a matchup of Cy Young winners, as Snell — who won the award in 2018 and 2023 — starts opposite of last year’s American League Cy Young winner, Tarik Skubal. Roberts said they are “two of the top-five pitchers in all of baseball.”

The next turn in the rotation will feature Yoshinobu Yamamoto, who started the Dodgers’ season opener in Japan. Roki Sasaki, who also pitched in the opening series, will take the mound Saturday.

Tyler Glasnow’s first start will be next week against Atlanta since he’s slated to start Tuesday against the Angels.