Team Japan is set to take the field on Saturday against Venezuela in the quarterfinals of the World Baseball Classic in Miami ... and Yoshinobu Yamamoto and his teammate -- L.A. Angels pitcher Yusei Kikuchi -- gave folks at the park an up-close look at their arms!!

TMZ Sports obtained footage of the duo hitting a nearby park not long after they landed in the 305 earlier this week ... which shows them working on their mechanics as they get set not only for more WBC action -- but also for the upcoming MLB season.

Luckily for the two, they seemed to avoid drawing any crowd as they did their thing -- perhaps the parkgoers were oblivious to the star power in their presence.

It's set to be a big night for Yamamoto, as he'll take the bump for Samurai Japan, with Ranger Suarez slated to toe the mound for Venezuela.

As of right now ... Kikuchi is scheduled to start the semifinal matchup, should they make it that far.

Once Yamamoto makes his final start of the event, he will remain with the squad for as long as they keep playing.