Boston won't make the playoffs so it doesn't matter, but the obvious answer is the Cavs. Lebron has never lost in the first round and is by far the best player in basketball, we have no one capable of guarding Love, and they have great scorers in the backcourt. Horrible matchup for Boston. But again Boston won't make the playoffs so it doesn't matter anyway.
Jeff Green has proven that he defends LeBron about as well as anybody in the league - he has pretty much shut him down on occasions in the past.
Kevin Love is grossly overrated, and this will be exposed this year when his scoring average drops from 26 to 18. He's the perfect example of a guy who scored by being a volume chucker on a bad team. Bosh's scoring dropped from 24 PPG to 17 PPG the instant he moved from Toronto to Miami, and he never averaged close to that again. Kevin Love is an unathletic 6'10" power forward who has zero post game and spends all of his time chucking up jumpers. Not really that much of a handful.
Irving? Yes, hes a very good player and a talented scorer, but Rondo at his best can dominate a game as much as Irving can.
As for Boston not having a go to guy...you could argue that, but Jeff Green has been an excellent clutch scorer the last couple of years and has hit some huge shots.
Dont get me wrong, Cleveland is a better team then Boston. That's obvious. But to the point where Boston should fear them? Absolutely not.
Kyrie Irving is not as good as Wade was in his prime. Nowhere near it. Im also going to say that Kevin love is not as good as Bosh was in his prime. The overall supporting cast IMHO were better in Miami then what LeBron had in Cleveland. IMHO Miami in the big three era were much scarier than Cleveland is now. At least Bosh was decent (and long) enough Defensively to hold his own against opposing bigs. The front court defense of this Cleveland team will be even worse than Boston's. They will be a painfully bad team Defensively, and I don't think they'll be good enough offensively to overcome that.
The top western conference teams will destroy the Cavs. They are no championship threat now or in the near future.
OkC, San Antonio, tge Clippers, all will destroy them.
Cleveland will struggle against Washington, Chicago, and probably even Brooklyn and Miami.