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Andy Murray faces the first test of his imperfect preparations for the ATP World Tour Finals when he takes on David Ferrer at the O2 Arena on Monday afternoon.
The world number two would normally have spent the build-up practising on hard courts but this year his main focus comes after proceedings are wrapped up in London.
Murray will then travel to Ghent where Great Britain will take on Belgium in the Davis Cup final on an indoor clay court.
Adapting to clay is a process that takes time for Murray so he spent four days last week playing on the surface at Queen's Club before having his first hit at the O2 on Friday.
He knows that may mean he is not at his best against Ferrer, although he appeared in very good nick during a practice set against Novak Djokovic on Saturday.
There has already been a Murray victory, with Jamie marking his debut in the doubles by defeating Australian Open champions Fabio Fognini and Simone Bolelli 7-6 (7/5) 3-6 11-9 alongside Australian partner John Peers.
It promises to be quite a fortnight for the brothers, who are set to play together in the doubles rubber in Ghent.
Jamie said: "It's exciting for me. It's lots to look forward to, obviously starting with today.
"I think we were both really looking forward to the match. It's a huge event for us, which we're really excited to be a part of. We worked hard all year to qualify for this tournament.
"We want to make the most of our time here. When that's done, then I'll think about Davis Cup."
Novak Djokovic and Roger Federer stamped their authority on the tournament with straightforward victories in the singles on Sunday.
Djokovic once again made a would-be rival look ordinary in a 65-minute 6-1 6-1 thrashing of Kei Nishikori, who later admitted he was "very ashamed" of the scoreline.
Life was tougher for Federer but he recovered from a poor start to defeat Tomas Berdych 6-4 6-2, with the Czech now having lost his opening match on each of the seven occasions he has qualified for the tournament.
Federer is making a record 14th consecutive appearance but admitted he was caught out by a touch of complacency.
He said: "It was one of the worst starts I've had in years. No first serves, two double faults, nothing coming from the baseline. So it was rough. But thankfully I was able to pick it up.
"I was playing very well in practice. When I came in, I kind of forgot it was a first round. I was a bit sluggish. I don't want to say too over-confident, but I thought it was going to be easier than that. It was a good lesson for me to learn."
Federer and Djokovic will now meet each other on Tuesday while the evening match on Monday pits Stan Wawrinka against Rafael Nadal.