I thought his name was Dennis Johnson too, don't feel bad.

Point guard for the Bird era Celtics.

Yep, it's where my mind immediately went when I saw the thread title. Forgot that he died, though. How, do you remember?

n February 22, 2007, at the Austin Convention Center, Coach Johnson had a heart attack and collapsed at the end of the Toros' practice.[22] After being rushed to a nearby hospital, he could not be revived and was later pronounced dead. Johnson was survived by his wife and his children.[22] Johnson's death was met with shock throughout the NBA. Among others, contemporary Celtics colleague Danny Ainge called him one of "the most underrated players of all time [...] and one of the greatest Celtics acquisitions",[22] and one-time rival Bill Laimbeer called him "a great player on a great ballclub"