World number one Roger Federer believes Andy Murray's game has not changed since their first meeting in the Thailand Open final in 2005.
Murray has won the last two of their three career meetings, including victory in the first round of the Dubai Championship on Monday.
"He's going to have to grind very hard for the next few years if he keeps playing this way.
"He tends to wait a lot for the mistake of the opponent," said Federer.
"He stands way far behind on the court and that means you've got to do a lot of running.
"I gave him the mistakes today but I think overall, over a 15-year career, you want to look to win a point more often than for an opponent to miss.
606: DEBATE
"That's what served me well over the years but who knows, he might surprise us all and do it for 20 years.
"I don't think he's changed his game a whole lot since I played him in the Bangkok final.
"Not that I'm disappointed but I really would have thought he would have changed it in some ways."
But Murray, who beat Federer 6-7 (6-8) 6-3 6-4 in Dubai, said he was surprised by Federer's comments.
"You do different things against different players." said the Scot.
"I feel quicker and stronger around the court. Mentally I feel like I'm better."
"You go and watch my match against Rafael Nadal at the 2007 Australian Open, and I was playing pretty close to the baseline in that match and taking a lot of risks because I think that's the right way to play against him..
"Against Federer I don't think that's the right way to play. I'm not going to play that sort of game against someone that defends as well as Federer does.
"My serve is clearly much better than it was two years ago. I feel quicker and stronger around the court. Mentally I feel like I'm better.
"But there are still some things in my game that I want to improve and it does take some time to put them into the match court. I feel like I've started to do that this year."
~RS~q~RS~~RS~z~RS~00~RS~)