"It is the biggest fight of the year," the 35-year-old said out in New York City on Wednesday ... before adding that it could be "the biggest fight in the last 10-plus years!"

Crawford might actually not be wrong ... even though Floyd Mayweather, Tyson Fury and Gervonta Davis have had some huge, headlining bouts since 2013 -- both Crawford and Spence have been must-see fighters for boxing fans all over the globe for the last few years.

The two are undefeated, have rare knockout power -- and are still considered to be in their primes.

And, Crawford tells us there's no way the match will let anyone down ... promising fight fans there will be "fireworks" in the ring when they get after each other next month.

As for who's going to come out victorious ... Bud insisted he's got it in the bag.

"I'm going to win this fight," he told us. "And I'm already the best fighter in the world!"