Offensively, Hayward is great. He can do it all and he is efficient. He is a 40% three point shooter and he shot over 50% on his two point shots. According to Synergy he rates out as the 9th most efficient player scoring 1.091 points per possession among players with at least 1000 possessions. However, Hayward is not coming to an offensively challenged team. The Celtics were the 5th best offense in the league according to Synergy and they now have the talent to be even better with Hayward and the drafting of Tatum out of Duke.
Defensively, Hayward is also quite good. He is strong, athletic, and he is smart. He is a high IQ player and he will do well to help Boston on the defensive end. He matches up as good as you can with Lebron James, but that is not saying much.
Hayward will be an All-Star for Boston next year and he will make them better, but they do not have enough to get past Lebron. I believe this because the Cavaliers do not get the credit they deserve for being a great team because of how much better the Warriors are, but Cleveland is a great team. They have so many shooters to surround the individual brilliance of James and Irving. They shot 44% from three in their series against Boston. Let me write that again, 44%. Now, they might not make as many shots next year, but the best player in the history of the league is still chugging along in his prime, which has lasted for a long time and I just do not see how Boston can get past them. They might be able to give Cleveland a challenge and they have definitely made themselves real contenders, but I do not see them beating Cleveland unless they sign Zaza Pachulia to step under Lebron's foot on a jumper.