SPRINGFIELD, Mass. -- Boston Celtics coach Brad Stevens engaged in a question-and-answer session Friday at the Basketball Hall of Fame, where a young visitor asked him pointedly why he traded away Isaiah Thomas earlier this week. "That's an excellent question," Stevens answered after laughter dissipated from fans in attendance following the unexpected hard-hitting question. The Celtics traded Thomas, Jae Crowder, Ante Zizic, and the Brooklyn Nets' 2018 first-round pick to Cleveland in exchange for Kyrie Irving on Tuesday. "Here's what I'll tell you: What [Thomas] did in Boston the last 2? years has been incredible. I said earlier what he's meant to me, what I think of him, how great he's been in the locker room, what kind of teammate he's been. Those are all really, really, really hard decisions. That's the hard part about being a professional basketball coach. I've stared at the wall many times and thought, 'Man, having guys in college for...