Rafael Nadal will miss November's season-ending ATP Finals in London and have surgery on an ankle injury. But he would have been keen to continue his winning run in the final regular-season event of the 2018 campaign before the ATP Finals in London. The Serbian will now become the first player since ATP rankings were introduced in 1973 to end the year at number one having started it outside the top 20.
"Unfortunately, I had an abdominal problem in Paris last weekend and I also have a problem with an ankle join that needs to be dealt with in the operating room today".
His decision means he will lose the end-of-season world No 1 ranking to Novak Djokovic.
What Anderson can not ascribe to, however, is progressing further than fourth in the world, with the points tally of current number one Novak Djokovic, withdrawn, but still current number two Rafael Nadal and number three Roger Federer beyond the South African's reach - come what might.
'I would reckon the Novak Djokovic group is the tougher one, ' said the German, who coached Djokovic for three years. I've been very close to making it for a number of years, but it just hasn't quite happened.
"This way I hope to be in top condition for next season".
Nadal withdrew from the following week's Cincinnati Masters and was then forced to bring a premature end to his US Open semi-final with Juan Martin del Potro due to a knee injury.
American John Isner takes Nadal's place at the eight-player event in London.
Anderson, who will make his first appearance in the tournament at the age of 32, beat Federer in the quarterfinals at Wimbledon, taking the final set 13-11. Djokovic might dwell arduously on the tennis courts of London as his draw seems plausibly hard to get through.
"What Novak has achieved this season has to go down as one of the great sporting comebacks", ATP Executive Chairman Chris Kerned said.