“I have kept myself in good shape, obviously I had an amazing team around me.”
Djokovic beat Nadal as Serbia won the ATP Cup over the weekend and Federer was impressed by the standard.
“I’m aware that at 38 I shouldn’t be the favourite, it should be someone probably in their 20s, but the three of us have been able to stay as the favourites which is great for us,” he added.
“Both guys are already showing great signs. I was watching a little bit of their ATP Cup match and thought that was a great match.
“Both guys, injury free, are always tough to beat.”