The intricacies of the ranking system may be becoming less and less clear by the day but Andy Murray improved his chances of qualifying for the season-ending Barclays ATP World Tour Finals yesterday by reaching the semi-finals of the Erste Bank Open in Vienna.
Having begun the week in 10th place in the Race to London, chasing one of the eight spots, Murray moved above David Ferrer into ninth after a straightforward 6-2, 7-5 win over Jan-Lennard Struff of Germany.
If anyone was confused by the Race before the week began, things won't have improved after Ferrer also reached the semi-finals in Vienna, beating Ivo Karlovic 7-6, 6-4 but still fell behind Murray. In theory, that should earn Ferrer the same points as Murray but in fact, the Spaniard has to reach the final this week to improve his points total. That's because Ferrer has already fulfilled his quota of six tournaments of 500 or 250 level, whereas Murray is filling out his quota this week and next.
Moreover, should Murray beat Viktor Troicki of Serbia in the semi-finals today, he will also move above Milos Raonic into eighth place. Having added Vienna and next week's event in Valencia to his schedule in a bid to take some pressure off the last qualifying event in Paris, Murray knows he just needs to keep winning matches. 
If he does that, the points will take care of themselves but first up is Troicki, a man rising up the rankings again after his 12-month ban imposed after he failed to take a doping blood test.
The Serb almost beat Murray at the French Open a few years ago and Murray, who was among the most critical of Troicki's actions in not taking his test on the required day, knows he will need to perform. 
"I've played well against him in the past," Murray said. "He's a very good athlete, he moves extremely well, and has a big serve. He always makes you work for matches. We have had some tough matches, close matches."
Four players - Novak Djokovic, Roger Federer, Rafa Nadal and Stan Wawrinka - are already assured of their places in London, although Nadal is a doubtful starter as he considers his options regarding surgery after appendicitis. 
Also, as a grand slam champion ranked in the top 20, Cilic is guaranteed a place in London thanks to another quirk of the rulebook, even if he finishes outside the top eight.
Tomas Berdych, No.7 in the Race, both won last night in Moscow and Stockholm. But Raonic looks likely to miss out and even Kei Nishikori, in fifth, could find himself in trouble after both he and Cilic pulled out of next week's event in Valencia.