We really need Horford to step up in game 7. If he doesn't deliver, I don't think we are going to the finals.
Al doesn't need to score a lot for the Celts to win, he needs to play smart. The Cavs are looking to keep Al from scoring. They are defending him with TT and doubling him. That makes it unlikely that he will have a big scoring game. He's not an elite offensive player to begin with, and if the defense focuses that much it is likely they can limit his scoring. What matters is how the Celts react to this. Forcing one on one post shots against TT is not good offense. TT defends Al well, the Cavs are happy every time Al tries to go one on one with him.
The Celts want Al to get going, so they are trying to get him chances to score, they shouldn't worry about that. Instead find the mismatches and attack them. If someone other than TT is on Al go to him. Attack Korver if he is out there. Get Brown and Tatum matched up against slower players and attack the rim. And most of all, don't try to get fancy. Avoid hero ball and don't try to make impossible passes. Turnovers have killed the Celts in the games that they have lost.