In the past, many professional baseball players were known for going out drinking after games, sometimes even breaking curfews. Shohei Ohtani stands at the complete opposite end of that culture.

Even during his time in Japan, senior players needed permission from manager Hideki Kuriyama before taking Ohtani out, reflecting how carefully his condition was managed. After games, both in Japan and in MLB, Ohtani rarely goes out, choosing instead to spend his time training—and sleeping.

From childhood, Ohtani openly said he was “good at sleeping.”
He slept in the car while his father drove him to practice, went to bed around 9 p.m. on days without training, and once asleep, rarely woke up during the night. During Little League training camps, while other children stayed up talking, Ohtani quietly kept his routine and went to bed early.

While such habits often fade with age, sleep has remained one of Ohtani’s top priorities even as a major leaguer. For him, resting well is not a luxury—it is part of what allows him to perform at the highest level.

Source

This quote comes from a Japanese book published in Japan and is not currently available in English.

Opening a Path, Crossing the Ocean: The True Story of Shohei Ohtani, p.70