Jayson Tatum, Matthew Tkachuk's Ex-Gym Teacher Says They Were Always Champ Material

Jayson Tatum and Matthew Tkachuk were destined to be world champions ... so says their former middle school gym teacher, who tells TMZ Sports he recognized long ago that there was something special about the two.

The Boston Celtics hooper and Florida Panthers left winger -- who both won their respective titles in the NBA and NHL this month -- both attended Chaminade College Preparatory School in St. Louis, MO as kids ... and Michael Derkits -- who also coached Tatum on the basketball team -- got an early look at their potential.

Derkits said Tatum and Tkachuk hit it off as soon as the former transferred to Chaminade as a 7th grader ... and he credits to them having similar personalities.

"They were fun-loving -- like to cut up, have fun -- kids," Derkits said. "It's funny to remember them back as 7th graders and see them progress throughout their lives to where they got to these last couple of weeks."

Derkits also reminisced on coaching Tatum ... raving about the skills he displayed as a kid.

"He was on a very talented team," he said. "But any time we needed a basket, or we needed something to happen, everybody kind of looked at Jayson, and he could make it happen."

As for Tkachuk -- who is probably still running around Florida with the Stanley Cup as we speak -- he didn't play ice hockey at the school because they didn't field a team. So when it was time for floor hockey in gym class ... Matthew gave it his all.

"I had a rule with [Matthew]," Michael said. "He could score one, but then he would have to get an assist because he literally could score one anytime he wanted."

While the two have been out of middle school for some time now, Derkits wants them to know how proud everyone is at their old stomping grounds.

"We're awfully proud you were able to achieve your goals, but even more proud of the men they are and how they represent themselves.