Doc sure does ... and tells TMZ Sports if there's anyone questioning his fighting ability, they need to watch that video!

Of course, the 55-year-old MLB legend is gearing up for a celebrity boxing match against 29-year-old comic Catfish Cooley on March 7 in Atlantic City.

Some people are concerned for Gooden since Cooley is a big dude who squats 600 pounds -- but Doc tells us HE CAN SWING, BRO!!

In fact, Gooden brings up that crazy brawl from August 1990 -- when Phillies pitcher Pat Combs threw at Doc and he charged the mound with bad intentions!

We found the clip -- and yeah, Doc's right ... he hit Combs with a solid right to the face that ignited a bench-clearing brawl! Good stuff!

Now, Doc says he's been training for his next fight and even hit up his old pal, Mike Tyson, for advice.

Turns out, Doc and Mike have been friends for decades -- remember when they kicked it together with Darryl Strawberry at Shea Stadium back in '86?

As for why Doc's fighting again, it's all about raising awareness for causes dear to his heart.

"I'm trying to do something positive to bring awareness to mental health as well as sobriety," Doc says.