After the stunning news Saturday that forward Jeff Green would miss the season because of an aortic aneurysm, yesterday the reaction of the Celtics was one of relief that the condition was detected, and gratitude that he will be able to continue his career next season. Players and coaches know how much they will miss Green's youth, versatility, and talent on the court, but that was secondary. They were far more concerned about the long-term health of the 25-year-old. "We were hoping we were wrong, obviously,'' coach Doc Rivers said before the Celtics beat the Raptors, 76-75, in an exhibition game at Air Canada Centre. "It's a tough one.