Roger Federer qualified for the semi-finals of the World Tour Finals on Thursday through his 14th victory without a loss against Spain’s David Ferrer as he beat the Spaniard 6-4, 7-6 (7-5) in their group match.

The Swiss world number two needed one and three-quarter hours to get the job done against a player who had won his last two indoor events, Valencia and Paris. Federer stands 2-0 in round-robin play this week. Argentine Juan Del Potro earned his first win as he beat Serb Janko Tipsarevic 6-0, 6-4 to keep alive his hopes of joining six-time year-end champion Federer in the final four with one set of matches still to play on Saturday.

Federer has totally dominated his fellow over-30 Ferrer in their career series, winning 11 of their matches in straight sets, including the last two year-end finals in London.

“I tried hard to not make it happen today,” Federer said of Ferrer’s dream of ending the overwhelming Swiss win streak. “You could feel that he’s confident, he’s on a run. I think even more it’s a great victory for me.” Federer needed 49 minutes to win the opening set, saving three break points in each of his first two service games and finding himself plagued by more than ten errors off his backhand side in the early stages.

Federer earned a break for 3-2 against the scrambling Spaniard whose game is the definition of durability. He concluded the set — which included a 12-minute third game — with another break as Ferrer netted a backhand.

The second set was no easier, with the epic progressing into a tiebreaker where Ferrer saved two match point before finally sending a return long over the baseline to take the loss.

“I thought the match was great, it was good intensity,” said Federer. “We both started a bit up and down at the beginning. We both picked it up in the second set, we started to have tougher rallies.

“Ferrer showed why he’s so tough to beat. He makes you hit the extra shot; he makes it physical. You know that mentally he’s not going to go anywhere.” Federer won with 28 winners and 39 unforced errors. He saved nine of ten break points he faced as he moved into the year—end semis for the 11th time in a dozen attempts.

He improved to 102—1 over the past decade against opponents aged over 30, with his lone defeat coming against Tommy Haas (34) in the Halle final in June.

Federer claimed his 70 match win of the 2012 season, in which he owns six titles to the seven of Ferrer. It marked his 14th win in Britain this season, with the loss to Andy Murray in the London Olympic final his only setback in that category.

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