Six-times champion Roger Federer has avoided an early exit from the ATP Finals as he rediscovered his form to outclass Dominic Thiem in straight sets.
The Swiss maestro needed just 66 minutes to dispatch the Austrian 6-2 6-3 while Kevin Anderson took two minutes less to crush Kei Nishikori 6-1 6-0 in Tuesday's early match.
Federer found himself with his back to the wall after an error-strewn loss to Nishikori in his opening round-robin match - his first straight sets defeat in 46 group stage matches at the season-ending showpiece.
Another loss would have made it impossible for him to reach the semi-finals for the 15th time in 16 appearances at the tournament.
Yet 48 hours later, the 37-year-old Federer looked much more like his old smooth self as he rebounded in style, to the delight of the majority in the packed stadium.
Thiem saved a break point in the opening game but he sent a forehand long to give Federer an early break that he never looked like relinquishing.
Two tame volley errors by Thiem gave Federer another break for a 5-2 lead as he cruised to the opening set.
Federer turned the screws to break again immediately in the second set and never looked in any danger.
"It feels good, I'm very happy I showed a reaction after the last match against Kei" Federer said.
"No match is easy here and it's not something I'm used to, losing and then coming back and playing again, but it's a great challenge and I'm happy with my attitude and how I played."
Federer will face South African Anderson in his final match in the Lleyton Hewitt group on Thursday.
Tournament debutant Anderson leads the group with two wins and would have been assured of a semi-final spot had Federer been beaten by Thiem or even dropped a set.
"Amongst the best I've played," Anderson told reporters when asked to rate his demolition of Nishikori.
"I felt I did a fantastic job throughout really."
Federer will likely have to avenge his Wimbledon loss this year by Anderson to reach the semi-finals, although all four players in the group could still mathematically progress.
"I hope it's not a match like Kevin played this afternoon," Federer said.
"It's never easy to play against him, especially indoors. He deserved that win at Wimbledon but hopefully I'll get my revenge."
