Macci was the coach of both Williams sisters during their formative years and left a huge impression on both. He still follows them closely and he thinks that Serena might not be fully done with tennis. It's something she herself has alluded to even though for now she's not focused on anything tennis-related.
He responded to several fan questions on Twitter answering them all in one Tweet:
McEnroe on what sets Federer apart from Connors and Sampras: "I don't think I've ever met anyone that just loved to go out there"
"Everybody is asking will @Serenawilliams play again. My answer is in doubles for sure with the one she has been skipping and holding hands with since age 9."