Japanese pitching sensation and major league target Roki Sasaki has been at less than his dynamic best so far this season, as his attempt to transition from a strikeout machine to a more efficient pitcher progresses slowly.

The Lotte Marines right-hander has a 3-2 record with a 2.56 ERA in six starts, striking out 41 batters over 38-2/3 innings, the strikeout ratio down significantly from 173 punchouts over 129-1/3 innings in 2022, the season he threw a perfect game.

Last Friday, the 22-year-old Sasaki, who is on the radar of a number of major league scouts, surrendered five runs on eight hits in 5-2/3 innings against the Nippon Ham Fighters.

Lotte Marines pitcher Roki Sasaki plays catch during pregame practice at Es Con Field Hokkaido in Kitahiroshima, Hokkaido, on May 12, 2024. (Kyodo)

Sasaki is trying to get more easy outs to keep himself healthy and in the rotation for a whole season for the first time in his pro career, instead of striking out one after another and ending up missing starts due to discomfort or injury.

This year, Sasaki is throwing his slider more often, saying, "My primary pitches were a fastball and a splitter, so it's better to have a type of pitch that goes to a different direction."

His slider has been used as a pitch to get both an early-count strike and a strikeout.

"A good slider will definitely refine his pitch arsenal," said Lotte manager Masato Yoshii, who pitched both in Japan and the major leagues during his playing career.

Lotte Marines pitcher Roki Sasaki (R) walks back to the dugout after ending the seventh inning against the SoftBank Hawks on April 23, 2024, at Zozo Marine Stadium in Chiba, near Tokyo. (Kyodo)

Sasaki's fastball has topped 160 kilometers (99.4 miles) per hour in only one game, against the SoftBank Hawks on April 23, this season.

He had constantly thrown over 160 kmh until last season, with the fastest hitting 165 kmh (102.5 mph).

"My velocity is down recently, and I am not getting tired. My fastball has stayed in the 150 range," Sasaki said after his first win of the season on April 7 against the Orix Buffaloes.

Sasaki might have saved some energy to last until the end of the season, but his fastball velocity has not ticked up even in important situations.

Roki Sasaki of the Lotte Marines pitches against the Rakuten Eagles on April 14, 2024, at Rakuten Mobile Park Miyagi in Sendai, northeastern Japan. (Kyodo)

He has played down concerns, however.

"I haven't gotten everything right yet, so I'll get better," Sasaki said.

In January, the native of Iwate, the northeastern Japan prefecture that also produced Los Angeles Dodgers two-way star Shohei Ohtani, voiced his ambitions for the future.

"I have wanted to pitch in the major leagues since I was a child," he said. "I've been having proper communication with (the Marines) every year. I believe the club understands it, too."

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