Manny Pacquiao Says He's Still Down To Fight Spence Once He's Healthy

Boxing fans still hoping to see Manny Pacquiao and Errol Spence square off in the ring ... don't give up hope just yet, 'cause the legendary pugilist tells us he's down to scrap with the 31-year-old once he's healed up.

Of course, 42-year-old Pacquiao and Spence -- the IBF and WBC welterweight champ -- were scheduled to box August 21 in Las Vegas ... but doctors discovered Errol had a torn retina -- a serious eye injury -- during pre-fight medical evaluations.

But, the fight isn't dead just yet.

TMZ Sports spoke to PacMan just minutes after the fight was canceled ... and we asked the 8-division world champ if he'd re-book the bout in the future.

"I have no problem [fighting Spence]. As long as he’s still physically fit, then okay," Pacquiao says.

Errol's out, but Manny -- coming off wins over Keith Thurman and Adrien Broner -- is still fighting later this month ... taking on the WBA Super Welterweight champion, Yordenis Ugas.

Ugas isn't regarded as a top pound-for-pound fighter like Spence, but MP says he isn't overlooking the 2008 Olympic bronze medal winner.