PERTH, Australia – Roger Federer found himself overmatched – just – by a younger and stronger-serving opponent on Wednesday, losing 7-6 (1), 6-7 (4), 7-6 (4) to 19-year-old Alexander Zverev of Germany at the Hopman Cup.

The 35-year-old Federer was playing his second match since returning from a six-month layoff because of a left knee injury. He led 5-2 in the first set, but ran into an opponent whose first-serve percentage exceeded 80 percent midway through the final set of the 2 1/2-hour match.

But it turned out to be a winning evening for Federer and Swiss partner Belinda Bencic. Bencic beat Andrea Petkovic 6-3, 6-4 in their singles match, and then Federer and Bencic combined in mixed doubles to beat Zverev and Petkovic 4-1, 4-2 in the Fast4 format.

“She (Bencic) carried us to victory, the player of the singles, the player of the doubles,” Federer said.

Earlier Wednesday, Kristina Mladenovic and Richard Gasquet won their Group A singles matches to give France victory over Britain. Mladenovic beat Heather Watson 6-4, 5-7, 6-3 before Gasquet defeated Dan Evans 6-4, 6-2.

Gasquet and Mladenovic later defeated Evans and Watson 4-3, 4-3 in mixed doubles to complete a sweep.

Temperatures during the opening match rose to as high as 40 degrees Celsius (104 degrees Fahrenheit), forcing both players to conserve their energy.

“It was definitely difficult,” said Mladenovic, who estimated she drank seven bottles of fluid during the match. “Sometimes you would like to try to put more intensity, but you have to be smart sometimes and maybe not run down every single ball.”

France and Switzerland, both 2-0, will play their final round-robin match against each other on Friday, with the winner advancing to Saturday’s final.

The United States, represented by Coco Vandeweghe and Jack Sock, have already qualified for the final from Group B after beating Czech Republic and Spain in its opening matches. On Thursday, the Czech Republic plays Spain and defending champion Australia takes on the Americans.