Photo/Illutration Pitcher Roku Sasaki of Japan speaks at a news conference at LoanDepot Park in Miami on March 19, ahead of a World Baseball Classic semifinal against Mexico. (AP Photo)

MIAMI--If Rōki Sasaki knows the perfect time for him to switch to the major leagues, he’s good at keeping a secret.

The 21-year-old right-hander pitches in a U.S. ballpark for the first time Monday night, when he’ll start for Japan in a World Baseball Classic semifinal against Mexico.

He became a sensation in his second season with the Pacific League’s Chiba Lotte Marines, pitching the 16th perfect game in Japanese history while striking out 19 against the Orix Buffaloes 6-0 on April 10. Seven days later, Sasaki was pulled after eight perfect innings against Hokkaido Nippon-Ham Fighters to limit his pitch count.

“He’s going to be a tremendous star in the big leagues whenever he gets here,” Mexico manager Benji Gil said Sunday. “He would be great at the big-league level right now.”

Looking larger than his 6-foot-2 frame, Sasaki worked out with his Japanese teammates at LoanDepot Park, home of the Miami Marlins. His only previous time in a U.S. ballpark had been in the same stadium, to record a commercial for Amazon.

“He is one of the pitchers that Japan is proud of,” Japan manager Hideki Kuriyama said through a translator. “This year and then next year is going to be a very critical year for him.”

Given the success of Shohei Ohtani, Sasaki is likely to be coveted by U.S. teams if and when he is posted by Chiba. Ohtani signed with the Los Angeles Angels at age 23 ahead of the 2018 season and emerged as one of MLB’s greatest talents.

“I think something will become clear when I’m going to shift over,” Sasaki said through a translator.

He’s also spoken with Ohtani about the transition to MLB, about “what team or what type of environment in the major leagues can provide.”

Sasaski arrived with the Japanese team at 4:30 a.m. EDT Friday after a 7,469-mile charter flight and is adjusting to a 13-hour time difference.

“I think I slept well on the plane, so I just don’t feel much jet lag on this trip,” he said.

Selected first in Japan’s 2019 draft, Sasaki made his Chiba debut in May 2021 and gained widespread attention with his startling starts in 2022. He tied the Japanese big-league record with 19 strikeouts in his perfect game, setting a mark with 13 Ks in a row. After throwing a 105-pitch complete game in Japan’s first perfect game since 1994, he was removed after 102 pitches and 14 strikeouts in his next start.

Pitching with Statcast tracking in the WBC, 21 of his pitches where over 100 mph in his group stage start against the Czech Republic at the Tokyo Dome on March 11, topping out at 101.9 mph. Sasaki induced 22 swings and misses among 66 pitches, throwing 36 sinkers, 28 cutters and two splitters. He got the win as Japan romped 10-2, allowing an unearned run and two hits over 3 2/3 innings while striking out eight and walking two.

Mexico figures be a tougher test with a lineup that includes Randy Arozarena, Rowdy Tellez, Isaac Paredes and Joey Meneses.

“101 and 102 miles per hour plays anywhere,” Gil said. “And then he has great secondary pitches, as well.”