Celtics' Jayson Tatum Jokes He's 'Not 19 Anymore' After Adding 10 Pounds

Jayson Tatum is finally growing up. 

The Boston Celtics star has long been in on a joke with the team's fanbase about staying 19 years old forever. As he enters his fourth year in the NBA, the power forward said he added 10 pounds this offseason to keep himself fresh this season. 

"I've gained probably about 10 pounds, so I think that's just obviously been in the weight room," Tatum told reporters Wednesday. "You know, getting older my body is starting to mature a little bit more. So I'm not 19 anymore."

Celtics fans on Twitter lauded the Duke product during his rookie season for his game being so polished despite the fact that he was "only 19." As the years went on, anytime Tatum's highlights were shown, the refrain of "he's only 19" would return on Twitter. 

Tatum joined in on the fun earlier this year in an exchange with Utah Jazz star Donovan Mitchell. 

Officially, the St. Louis native is 22 years old, but he'll always be a teenager to Celtics faithful.