Roger Federer came out on top in his highly anticipated match-up with Serena Williams to help Switzerland clinch their Hopman Cup tie against the United States 2-1.
Federer gave Switzerland a 1-0 lead with a 6-4 6-1 win over Frances Tiafoe.
Williams then overcame a case of the first-set wobbles to post a 4-6 6-4 6-3 win over Belinda Bencic, levelling the tie.
But the mixed doubles clash was always going to hog the spotlight given it was the first time Federer had faced off against Williams in a competitive match.
But the fact it would also decide the tie winner added extra intrigue.
The US, who lost to Greece in their opening tie, needed to beat Switzerland to keep their title hopes alive.
But it was Switzerland who came out on top, winning the Fast4 format 4-2 4-3 (5-3) in 46 minutes.
"I was so excited, and literally it was the match of my career," Williams said of her joy of playing Federer.
"Just playing someone so great, and someone you admire so much, and a match that actually means something - it's not often that happens.
"It was really cool to play someone still in their prime, like me, both in our primes. I'm kind of sad it's over."
Federer and Williams took a selfie together after the match to mark the occasion.
"I was nervous returning (her serve) because you just don't know," Federer said of Williams.
"People talk about her serve so much and I see why - it is such a wonderful serve because you just can't read it, you don't see until the very end.
"It was great great fun. She is a great champion and you see how focused and determined she is and I love that about her."
Switzerland, who have won both of their ties, will guarantee themselves a spot in the final with victory over Greece on Thursday night.
But even a 2-1 loss might be enough for them to sneak through.
Williams enjoyed a strong opening service game in the mixed doubles, with two of her serves proving too difficult to handle for Federer.
But the class of Federer shone through during the quick-fire rallies.
Williams grabbed at her right shoulder several times during the match, but said it wasn't anything to worry about.
"It was such a quick turnaround (from yesterday's match)," Williams said.
"I didn't have enough time to reload the cannon. It's totally normal. I've just got to rub it out."
Earlier in the night, Williams raced out to a 3-0 lead in the opening set before losing six of the next seven games.
But Williams lifted in the big moments, breaking Bencic in the final game of the second set to level the scores, before powering to victory in the third.
Federer was at his clinical best in his singles match, winning seven straight games at one point to set up the win.
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