Shanghai: Shanghai Masters pull-outs from Novak Djokovic and Roger Federer have crushed hopes of a mouthwatering four-way battle but opened the door for defending champion Andy Murray to edge up the rankings.
In a major blow for the tournament, organisers announced on Friday that world number one Djokovic had withdrawn after failing to recover from a troublesome back injury.
The Serb apologised for the withdrawal, which deprives the event starting on Sunday of another of its top stars after 16-time Grand Slam winner Federer decided to skip the tournament to rest and deal with nagging injury problems.
It means Britain's Murray, who beat Federer in last year's final in Shanghai, will only have Spanish world number two Rafael Nadal for company among the four players who have exerted an iron grip on the men's tour.
"I am sorry not to be playing in Shanghai, one of my favourite tournaments, but I have not recovered yet from my injury," Djokovic said in a statement.
"I did another check this week and the results are not good so I need to continue my rehabilitation."
Djokovic's back injury flared during his US Open final against Nadal and last month he was in tears as it forced him to concede the crucial fourth match of Serbia's Davis Cup tie against Argentina.
The loss of Djokovic is a major blow to the tournament after a stellar season for the Serb, in which the 24-year-old has lost just three matches against 64 wins.
His staggering run has brought him 10 titles including the Australian Open, Wimbledon, the US Open and five Masters 1000 trophies.
Former world number one Federer had earlier withdrawn from the event because of injury, with the Swiss insisting he needs to rest after a gruelling year.
But the absence of Federer and Djokovic has eased the path for Nadal and Murray, who both come into the tournament in good form.
Murray hammered Donald Young of America 6-2, 6-0 last week to win the Thailand Open, his third title of the season.
During the tournament, Murray, whose career-high ranking is second, spoke of his desire to replace Federer as world number three. The Scot now has a golden chance to make the most of the Swiss great's absence.
Spain's Nadal, chasing his 20th Masters title, played a key role in his country's victory over France in the Davis Cup semi-finals, romping to two singles wins.
The Big Four have already qualified for the year-ending ATP World Tour Finals in London as the season enters its final stretch but there are still four other berths up for grabs for the showpiece event.
The other qualifying slots are currently occupied by Spain's David Ferrer, America's Mardy Fish, France's Jo-Wilfried Tsonga, who won in Metz last month, and Tomas Berdych of the Czech Republic.
But the likes of Spain's Nicolas Almagro and Sweden's Robin Soderling are among a clutch of players still in the running for the year-end tournament with points at a premium as the number of tournaments runs out.