Croatian Marin Cilic celebrates taking the opening set against American player Jack Sock, during day three of the ATP World Tour Finals being played at the O2 Arena in London, Tuesday Nov. 14, 2017. ( John Walton/PA via AP)
Croatian Marin Cilic celebrates taking the opening set against American player Jack Sock, during day three of the ATP World Tour Finals being played at the O2 Arena in London, Tuesday Nov. 14, 2017. ( John Walton/PA via AP) Credit: John Walton

London — A day after the ATP Finals lost Rafael Nadal to injury, Roger Federer lifted spirits at the O2 Arena by extending his stay to the weekend.

The 19-time Grand Slam champion guaranteed his place in Saturday’s semifinals by defeating Alexander Zverev, 7-6 (6), 5-7, 6-1, on Tuesday.

With Novak Djokovic and Andy Murray also absent due to injuries, the top-ranked Nadal’s withdrawal on Monday left Federer as the only member of men’s tennis’ “big four” in the tournament.

“It was nice to be able to show maybe that quality of mine, that I can dig out these matches, these points time and time again, stay mentally tough,” Federer said. “In the third I started to play better. It was a tough match from the beginning till the end.”

Zverev, who won his opening match against Marin Cilic, will face Jack Sock on Thursday to decide who will join Federer in the final four. Sock defeated Cilic in the early match, with Federer’s victory eliminating the Croat.

After an opening set dominated by serve went to a tiebreak, Federer came from 4-0 down and saved a set point to take the lead.

His grip on the match quickly tightened as a distracted Zverev made two double faults to gift a break in the opening game of the second set.

However, the 20-year-old regained his poise and took advantage of a dip in Federer’s first serve percentage to break back and then repeated the feat to force a deciding set.

Sock’s 5-7, 6-2, 7-6 (4) victory was the United States’ first at the event in 10 years.

Skiing

Frances’ Poisson May Have Hit Tree

Paris — The French Ski Federation said an early investigation into the death of David Poisson suggests the safety netting failed and he hit a tree.

The 35-year-old Poisson died on Monday while training at the Canadian resort of Nakiska, which staged Alpine skiing races of the 1988 Olympics.

The federation says in a statement on Tuesday that Poisson lost a ski then fell heavily, and “might have hit a tree after going through the safety netting.”

Poisson, who won the downhill bronze medal at the 2013 world championships, was training for World Cup races in North America.