The former Alabama quarterback hit up the private D1 Training facility with a VERY small group of people (less than 10) and ran 75 plays to show off his arm strength and quickness.

Watch the video ... he moves and throws like the Tua you remember in college -- and he's clearly hoping the footage will ease any concerns teams have about his health.

Remember, Tua suffered a devastating season-ending hip injury (a dislocated hip with a fracture to the posterior wall) during a game against Mississippi State back in November.

Since then, it's been a long road back -- and with the COVID-19 pandemic preventing teams from getting a thorough in-person look at the QB before the upcoming NFL Draft, he's trying to keep his stock high by proving he's good to go.

One person who was impressed -- ex-NFL QB Trent Dilfer -- whose been working with Tua and says the kid has a better arm than Hall of Famer Dan Marino.

Just last week, Tua told the NFL Network he feels "100%" -- adding, "I feel like if there was a game today, I'd be able to go out and perform the same way I was able to perform in previous years."