Murray faces rankings fall back to No 4

Scot climbed to No 2 this year but wrist injury means Djokovic can overtake him

Murray will return in Valencia (Getty)

Andy Murray's willingness to risk his injured left wrist in order to play for his country may well cost him his world No 3 ranking. The 22-year-old Scot has withdrawn from next week's Shanghai Masters on medical advice while he recovers from the injury, which he aggravated playing in Britain's Davis Cup tie against Poland in Liverpool last month.

Murray, who briefly rose to world No 2 in the summer, had been due to defend 1,000 ranking points in China, Shanghai having effectively taken the place in the calendar previously occupied by the Madrid Masters, which he won 12 months ago. That is a big chunk out of Murray's current total of 8,390 ranking points and puts Novak Djokovic within striking distance of reclaiming the No 3 spot after being overtaken by the Scot in the spring.

Djokovic, who could pick up points this week at the China Open in Beijing, has good memories of Shanghai, having won the Tennis Masters Cup there last November. The Serb has fewer points to defend than Murray both next week and at the year's final Masters event in Paris next month.

While Murray's injury was never as severe as the damaged tendons in his right wrist that forced him to miss the French Open and Wimbledon in 2007, the inflammation causes pain when he hits his two-handed backhand, his most damaging shot. He sustained the injury in the build up to the US Open two months ago and suffered a recurrence at Flushing Meadows. Although he made light of it at the time, it seems likely that the injury played a significant part in his lacklustre performance in losing to Marin Cilic.

If Murray had been tempted to pull out of the following week's Davis Cup tie, he was also aware of the criticism he had received in the past, not least from his brother Jamie, for withdrawing from national duty. Despite Murray's efforts against Poland – he played three days in succession and won both his singles rubbers – Britain still lost. There were times when the injury was clearly causing him considerable pain and he has rested the wrist since, although it has not stopped him from training.

Murray pulled out of this week's Japan Open to give himself every chance to recover in time for Shanghai, but the earliest he will reappear will now be in four weeks' time in Valencia. He is then due to play in the Masters in Paris before returning to London for the Barclays ATP World Tour Finals, the end-of-season showpiece at the O2 Arena beginning on 22 November.

His performances in the Masters events, which carry the most ranking points after the Grand Slam tournaments and World Tour Finals, have been crucial in Murray's rise. Only Rafael Nadal can better his Masters record over the last 12 months, the Scot having won three of the nine titles and failed to reach the quarter-finals only once.

Players care about rankings not only because they reflect their abilities but also because they can earn easier draws in tournaments. While slipping from No 3 to No 4 would have no significant effect on Murray, dropping down another place would mean that to win some events he might have to beat the world's top three players in the quarter-finals, semi-finals and final.

Murray will be hoping principally to keep his place in the top four come the Australian Open in January. He will be aware that Juan Martin del Potro, the current No 5, is only 1,835 points behind him and has only quarter-final points to defend in China. Roger Federer, the world No 1, has also pulled out of Shanghai, citing exhaustion.

* Heather Watson, Britain's US Open junior champion, was beaten 2-6, 6-4, 6-2 by Kristina Mladenovic, the French Open junior champion, in the second round of the Aegon Pro-Series tournament in Barnstaple yesterday. Naomi Cavaday, the British No 5, went down 6-4, 6-2 to Russia's Ksenia Pervak, the top seed.