Jayson Tatum has seen plenty of games featuring Cleveland’s LeBron James. And in the Boston Celtics’ preparation for Tuesday night’s matchup, the 19-year-old rookie had seen plenty of James on film. But facing him, up close and personal, was something entirely different. “He’s way bigger than I thought,” Tatum said. “He’s way better than I imagined. That’s the reason why he is who he is.” James’ play was among the key factors in Cleveland handing Boston a 102-99 loss on Tuesday night. But Tatum showed he too has some big-time potential by finishing with a double-double of 14 points and 10 rebounds which included some nifty drives to the basket as well as showing the ability to hold his own on the glass in terms of rebounding the basketball. The last Celtics rookie to post a double-double on opening night? That was Larry Bird back in 1980, helping the Celtics to a 114-106 win over the Houston Rockets. What’s even crazier? Bird had 14 points and 10 rebounds in that Rockets game, too.