In Japan, there is a youth baseball tournament organized by Nippon Professional Baseball known as the NPB Junior Tournament, where teams made up of fifth- and sixth-grade players represent each of the 12 professional clubs.

In 2006, the Rakuten Junior team won the tournament.
Shohei Ohtani, then a sixth grader, was not selected as a member of that team.

At the time, Ohtani stood at 165 centimeters.
While that was tall for his age, the Rakuten Junior roster included a pitcher who was already 175 centimeters tall.
Ohtani was frustrated that he could not throw a better ball than that player.

Even so, he never felt that he would fall behind in the long run.
He believed, without hesitation, that he would eventually grow to 190 centimeters.

As long as his skills developed alongside his physical growth, he felt there was no need to worry.
Losing at that moment did not matter.

Just as he believed, Ohtani grew to nearly 190 centimeters by the time he entered high school,
and went on to succeed in professional baseball and eventually Major League Baseball.
His generation would later come to be known as the “Ohtani generation.”

No one can predict exactly when or how much a person will grow.
But Ohtani carried an unshakable confidence about his future,
and that confidence became a quiet source of strength as he continued to develop.

Source

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

Baseball Soaring Years II – MLB Edition 2018–2024: Long Interview with Shohei Ohtani, p.109