Sasaki's nickname is a tribute to legendary Japanese starting pitcher Daisuke Matsuzaka, who was known as the "Monster of the Heisei," referring to different eras of the Japanese calendar. The 23-year-old lost both his father and grandfather during the 2011 Tohoku earthquake and tsunami.

Sasaki, nicknamed in Japan as "the Monster of the Reiwa Era," struck out 11 batters in 7 and ⅔ innings with a 3.52 ERA during the 2023 WBC. In Japan's Nippon Professional Baseball, he struck out 129 hitters in 111 regular-season innings for the Marines in the 2024 season.

Along with Blake Snell – signed to a five-year, $182 million contract in December. And Yoshinobu Yamamoto, who was posted one year ago after seven dominant seasons in Japan, signed a $325 million contract – and was the starting pitcher for four of the Dodgers’ 11 postseason wins.