Andy Murray will drag his weary body through another tough test at the ATP World Tour Finals as an explosive season finale draws ever nearer.
Having beaten Marin Cilic and Kei Nishikori, Murray only needs a set against Stan Wawrinka on Friday to guarantee his passage through to the semi-finals at the O2 Arena for the first time since 2012.
That will not be easy in itself, with world number three Wawrinka showing much better form in beating Cilic on Wednesday than he had in his limp loss to Nishikori.
The Swiss, meanwhile, knows that a straight-sets win over Murray would maintain his record of always reaching the last four.
It may not be essential, but Murray has plenty of incentives to win his final group match - not least the knowledge that doing so would mean he could not face Novak Djokovic until the final, setting up a straight shoot-out for world number one.
Victory would also equal the career-best winning run of 22 matches he set earlier this summer.
The Scot needed three hours and 20 minutes to see off Nishikori but was back on court early on Thursday morning for a practice session.
He said: "Obviously it's important to win matches to give yourself the best chance to go through.
"Two hundred points for each match here is quite a lot, as well. Obviously that increases as you get into the semis, potentially in the final. It could come down to a match between me and Novak. Who knows what's going to happen the next few days.
"Just from my side, I'll concentrate on trying to win my own matches, get through as many as I can, make it as tough as possible for Novak to jump me."
Murray might already have all-but sealed the year-end number one ranking had one of his finest achievements been recognised with ranking points.
Unlike four years ago, when Murray won his first Olympic gold in London, the ATP did not sanction points to be awarded in Rio.
With Djokovic having lost in the first round to Juan Martin del Potro, the player Murray went on to beat for gold, it could have made all the difference.
"I think there should be points at the Olympics," said Murray.
"For a lot of the players, we would play it regardless of whether there's points or not. Winning a gold medal, that's been the proudest moments of my career.
"It's nothing to do with me trying to get to number one or not. I think a lot of the players feel the same way."
Prior to Wednesday's epic encounter with Nishikori, Wawrinka was the last top-five player Murray had beaten, all the way back in the French Open semi-finals in June.
That was one of the Scot's most impressive performances of the season and ended a run of three straight losses to Wawrinka, including at the same stage here last year with qualification at stake.
Wawrinka, who faces a battle to hold onto the world number three ranking, said: "All I know is, if I want to have a chance to qualify, I need to win. That's all I'm trying to do.
"I'm going to try to play my best tennis, to beat the world number one. It's going to be a tough match. We played each other many times.
"He's playing his best tennis so far. It's going to be interesting. I'm happy to play here in front of his home crowd. I'm sure it's going to be a great atmosphere."
Should Murray win his group, he would play the winner of Thursday evening's clash between Milos Raonic and Dominic Thiem in the semi-finals.
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