MELBOURNE, Australia — Novak Djokovic and Andy Murray have known each other for a quarter of a century. They played from the age of 12, meeting 36 times as professionals, including 10 Grand Slam matches . Yet they’ve never been able to talk shop and freely trade all sorts of thoughts — about tennis and otherwise — until now.

Novak Djokovic has been pleasantly surprised by the professionalism of new coach Andy Murray in the leadup to the Australian Open but said sharing his deepest thoughts with his former rival had initially been a challenge.