The Blues captain's performances have been the subject of criticism this season, with some questioning if he still has the pace to compete in the Premier League.
Terry has also had to deal with allegations of racially abusing Anton Ferdinand and is due in court next week.
Villas-Boas, however, has backed his skipper to ignore the negatives and continue to perform on the pitch.
He said: "John Terry is one of the greatest central defenders in the world, maybe one of the best ever in the game.
"His qualities are amazing and he's a player who almost guarantees you success in terms of individual and collective performances.
"He is a player we hold in the highest esteem and a person I have great empathy with and great respect for. Whichever route our lives will take, JT is a person I will always hold as a friend.
"As a player he has been extremely successful in the world game. He was involved in my knowledge-making and in my progress as a manager.
"All the top players have the ability to concentrate fully on the task they have to do in a game."
