Andy Murray has said that matches against Novak Djokovic can be "a little bit tiring" ahead of their meeting in the ATP World Tour Finals tomorrow.
Murray beat Tomas Berdych in his opening match of the tournament, while Djokovic overcame Jo-Wilifred Tsonga.
Murray told Sky Sports News: "For me anyway there's an understanding of how much you have to put into the match to win it.
"Both of us are very good retrievers, so often the points will go on a lot. Sometimes you feel like you need to win the point two or three times, which is tough and can be a little bit tiring.
"But we've played each other enough to know what to expect. We do practice with each other quite a lot, too. But it's never quite the same as the matches, that's for sure."
The pair have played six times this year, winning three matches each.
