I think it depends how you want to define athleticism. Is it just explosiveness and strength? Or can it also be reaction, balance, and endurance? I don’t think Tatum’s strength/explosiveness is anything more than average for an NBA player. But he seems to have a very good reaction time, which allows him to gain a quarter-to-half step when going for rebounds. He’s got terrific balance, which helps make his pump fakes more effective, either to shoot or drive after the fake, and also to absorb some contact at the rim. And he leads the team in minutes played this season, without looking winded at the end of games.