Paris: Juan Martin del Potro's dream of reaching the ATP Finals was ended by John Isner of the United States in the Paris Masters quarter-finals here, while Serbian qualifier Filip Krajinovic enjoyed a walkover after year-end world No. 1 Rafael Nadal announced his withdrawal due to a knee injury.

Recording 20-4 in hard-court season since the US Open, the Argentine Potro was just one win away from securing the last spot for the Finals on Friday, reports Xinhua news agency.

However, Isner, also in hope of reaching the season-ending tournament in London, showed his winning mentality with a 6-4 victory in the first set. Thanks to high winning percentage on first serves from the two players, the second set was in balance after 12 games, thus being forced into a tie-break. Then Isner suffered a terrible double fault, and had to concede the tie-break 7-5.

Isner broke in the third game of the decider, and took his chance to set it 6-4. After overcoming favourite contender Potro, Isner could clinch the last spot for the Finals if he manages to lift the trophy in Paris this Sunday.

"Going into this tournament, I wasn't thinking about it (the Finals) at all," admitted Isner. "I was sort of thinking about what football games I'm going to watch back home when this tournament is over," he joked.

Maybe it's a bit surprising for Isner, as his opponent in the semifinals will not be title favourite Nadal. The Spaniard had to put off his quest for the first Paris Masters title due to knee concern. His previous best record at the Paris Masters came in 2007, when he finished runner-up behind Argentina's David Nalbandian.

Actually Nadal injured his right knee before the decider against Uruguay's Pablo Cuevas in Thursday's round of 16. He had bandage on his right knee when returning to the court. "Yesterday the pain during the match was too much, but it was not the moment to stop. I don't like to stop in the middle of the match.

"And especially during the match, thinking that I have some hours in between to do some treatment, that's what I did yesterday with the doctor here," explained the season-ending world No. 1.

Wild card Julien Benneteau gave home crowds every reason for joy, as the Frenchman upset third-seeded Marin Cilic of Croatia 7-6 (5), 7-5, reaching his second ATP Masters 1000 semifinal.

"I believe that win ranks quite high in everything I achieved in my career. Individually, I believe it's my most beautiful emotion ever," commented Benneteau. Next up against Benneteau is another American player Jack Sock, who saw off Spain's Fernando Verdasco in full sets.(IANS)