Andy Murray will hope the complexities of the round-robin system do not come back to bite him again as he bids to reach the semi-finals at the Barclays ATP World Tour Finals in London.
The first year the tournament was held at the O2 Arena three years ago, Murray appeared to have done enough with his two round-robin victories but results conspired against him and he ended up missing out by one game.
"We're not really used to it in tennis because we play knockout everywhere else," said Murray. "But that's just the way this tournament's always been."
Things are not quite so complicated this time around but there are still possible scenarios in Group A where the Scot could beat Jo-Wilfried Tsonga on Friday evening and not qualify or lose and go through.
Murray will at least know what he has to do as Novak Djokovic and Tomas Berdych play earlier in the day, and a win for the world number one would mean any victory for Murray would be enough. But if Berdych beats Djokovic in straight sets then the British number one is in danger even if he wins, with a set for Tsonga enough to eliminate Murray.
The Scot's path was made more tricky by his loss to Djokovic on Wednesday but he has no complaints about the system and insists it will not weigh on his mind.
"There's no point in changing it. That's the tradition of this tournament. It's absolutely fine. You need to try and view it like it's a knockout and try to win the first couple of matches, get yourself safe if you can. We should be able, as professional sportsmen, to deal with all those sorts of situations, be able to focus and concentrate regardless of the situation."
Murray's British compatriot Jonny Marray is already through to the last four with doubles partner Freddie Nielsen after they won their opening two matches to ensure they will top their group. On Friday they have the luxury of a dead rubber against Sweden's Robert Lindstedt and Romania's Horia Tecau, who they beat in the Wimbledon final.
Roger Federer became the first singles player to qualify on Thursday when he defeated David Ferrer 6-4 7-6 (7-5). It is the 10th time in 11 years that Federer has made the semi-finals while he is going for his seventh title and third in a row at the O2 Arena.
A win for Juan Martin Del Potro over Federer on Saturday would put the Argentinian through as well after he defeated Janko Tipsarevic, who has been struggling with illness, 6-0 6-4.