I'd say that right now the Astros are the best team in baseball, and the Sox have some big question marks as the playoffs approach: Can Sale stay healthy? Can the bullpen gets its act together? And can the offense rediscover the consistency it had in the first half of the season?
Pats should be in the mix for title contention, but their defense is atrocious and that may not be fixable—and the offense, no matter how great, may not be able to surmount a terrible D (see last year's SB).
The Celtics seem stacked, for sure, but staying healthy is key, and that's not something they've been able to do in recent years.