When Shohei Ohtani takes the field for Samurai Japan, you might be surprised by the number on his back. The global superstar is known by his iconic No. 17 on the Angels. But with Team Japan, he's dropped down one digit.

"I'm not overly concerned about what number I'm putting on," Ohtani said in a press conference earlier this month. "But I've always had a number of 16 when playing for Team Japan."

Yes, the answer is pretty simple: When Ohtani has suited up for his country, he has worn No. 16. So, the slugger and ace has simply chosen to stay with it.

But there could be a little more to it, as well. In the 1960s, the Yomiuri Giants began issuing its ace pitchers the No. 18. Since then, it's become a trend that's closely followed by many Japanese pitchers. Daisuke Matsuzaka wore No. 18 with the Red Sox, Hiroki Kuroda wore it throughout his career, and Kenta Maeda even had that uniform number stipulated in his contract.

Mitch Garver had to swap numbers, so Maeda could have it:

“Hey, if it means he’s going to pitch like an ace, I’ll give him a lot more than that,” Garver joked at the time.

Masahiro Tanaka didn't wear No. 18 with the Yankees -- he chose No. 19 instead -- but wore 18 in Japan.

As for Japan's current No. 18? It's back-to-back Sawamura Award-winner (the Japanese version of the Cy Young), Yoshinobu Yamamoto. Perhaps Yu Darvish has seniority over him, but has always worn No. 11, letting the future star of Team Japan wear the number.

So, as for Ohtani, it's likely a little bit of tradition and a little bit of random luck of the draw: It certainly doesn't seem like a coincidence that he always wears a number so close to the traditional ace's.