Paul Pierce and Rajon Rondo recently said the Celtics had to become more disciplined defending.

“I think they’re right,’’ Doc Rivers said. “It’s something we’ve talked about all year but it’s difficult when you don’t have practice times, you don’t have the right guys on the practice floor.

“They have to trust each other more, this year more than ever, defensively and offensively. You can’t, defensively, go double or go switch on a play where we haven’t worked on it. Usually, with a lot of practice, you can get away with it because someone will cover up for you. Execution is very important and probably more so this year than any year I’ve ever coached.’’