The former St. Louis Cardinals star -- who was the last MLB player before Ohtani to have huge success as both a hitter and pitcher -- broke it all down for TMZ Sports this week ... explaining Shohei is just that electric.

"Look, there’s nothing the guy can’t do on a baseball field," said Ankiel, who Ohtani just passed on the all-time MLB home run leaderboard.

"Watching what he’s doing, it definitely is must-watch TV ... every time I see it, I stop."

Ankiel says because of Ohtani's ties to Japan ... the incredible year he's having is bringing eyeballs to the sport that may have never been brought otherwise.

"I think you’re going to have a lot of kids who are seeing him maybe for the first time on the All-Star Game, looking up to that and going out in the backyard and trying to hit like Ohtani, and pitch like Ohtani and try to be that growing up," Ankiel said.

"I think it’s fantastic."

Ohtani has a ridiculous 32 home runs already this season with a stellar .279 batting average ... and he's the clear-cut favorite for AL MVP at the moment.

Oh, and by the way, he also has a 3.49 ERA and a 4-1 record as a pitcher.