Novak Djokovic has admitted to being wary of Roger Federer's appointment of Ivan Ljubicic as part of his coaching set-up.
The Croatian, who previously coached Milos Raonic, is a friend of Djokovic but agreed to join Federer's staff in December following his split with Stefan Edberg.
The move has been seen as an attempt from Federer to break Djokovic's dominance of the ATP Tour, after the world number one won three grand slams in 2015.
Asked if he would find it odd to see Ljubicic working so closely with Federer, Djokovic said: "Honestly, yes, but we are professionals.
"[Ljubicic] knows my game, he knows the game of all Roger's opponents, and I think that's one of the reasons why Roger has hired him.
"Whether it's going to work or not, that's something to see for all of us, but I wish them all the best.
"Ivan is a great guy, very calm, very composed, and I am sure Roger knows why he hired him."
Nevertheless, Djokovic remains focused on his own game and is aiming to win every competition he enters this year, starting with the Qatar Open which begins on Monday.
"Grand slams and the Olympic Games are the priority of the season," the Serb added.
"But it's a long season, so I can't really predict what's going to happen or guarantee if I am going to win any of the grand slams or all four.
"Of course, I am going to try to win every tournament and every grand slam that I play in, that's kind of the mindset that I have."