LONDON (The Guardian‎) - Andy Murray’s chances of qualifying for next month’s ATP Tour Finals received a significant boost on Friday night when Rafael Nadal pulled out of the season-ending tournament. The British No1 had earlier strengthened his cause by beating Kevin Anderson to secure a place in the semi-finals of the Valencia Open.

Nadal announced he was to undergo appendix surgery on 3 November, six days before the start of the tournament in London for which eight players qualify. The Spaniard’s withdrawal has in effect promoted Murray to the No7 spot in that race.

"It’s the day to say goodbye for the season,” Nadal said after suffering a shock 6-2, 7-6 (7-4) defeat by the 17-year-old Croatian Borna Coric in the quarter-finals of the Swiss Indoors in Basel. "I’m not going to play Paris and London. I am not competitive enough to do that.”

Nadal has struggled with appendicitis this month and had earlier announced he would not be playing at the Paris Masters.

His emphatic defeat by Coric provided more proof of the Croatian wunderkind’s potential. The teenager, called "Baby Djokovic” because of similarities with the world No1 Novak Djokovic, gave his off-color opponent a torrid time.

Nadal was unrecognizable in the first set as he offered no resistance. His timing improved marginally in the second but twice Coric served to stay in the set and held his nerve when a loose forehand from his opponent gave him two match points.

Coric needed only one of them, forcing a weary Nadal to send a defensive forehand wide.

Before undergoing surgery, Nadal will receive treatment for a back issue that has bothered him since the Australian Open in January, when he was severely compromised in his final defeat by Stan Wawrinka.

"I need to work on my back a lot,” said Nadal. "Since Australia I’m not 100% recovered. That needs time and a period of five weeks to work hard again. I need to try to fix all the things that bother me. I’m going to work for one month in December and I will be back at the start of 2015.”

It has been a season of highs and lows for Nadal, who won a ninth French Open title in June but was then forced to miss the US Open because of a wrist problem.

No sooner had he returned from that than the appendicitis struck, and Nadal said: "Every day I felt a little bit more tired. I tried to practice to try to get fit but it was not possible. It’s difficult to play and compete when you’re not able to practice weeks in a row.

"I’m not a player who competes to try to be in quarter-finals. I try to compete with chances to win tournaments and today is not the day that I can work for that. It’s been a very hard year for me mentally and physically, too.”

Murray survived a test of his credentials to see off Anderson in three sets and will play David Ferrer in the last four. The Scot lost the opening set on a tie-break but fought back bravely to claim a 6-7, 6-4, 6-4 victory which kept the players on court for two hours and 43 minutes.

Murray was playing in his fifth successive tournament and tiredness appeared to be creeping up on him as he at times looked heavy-legged and reluctant to move around the court. But he found the energy to secure victory on his fourth match point thanks to Anderson’s exhausted-looking forehand into the net.

Ferrer’s win over Thomaz Bellucci was the 600th of his career. He beat the Brazilian 6-1, 6-2 and joined Lleyton Hewitt, Nadal and Roger Federer as current players to have hit the 600 mark.