KEY BISCAYNE, Fla.-Roger Federer lost his second consecutive match and the No. 1 ranking Saturday.
Big-serving Australian Thanasi Kokkinakis, a qualifier ranked 175th, rallied to upset Federer 3-6, 6-3, 7-6 (4). The 36-year-old Federer had been the oldest No. 1 man ever, but he'll lose that spot to Rafael Nadal when the new rankings come out April 2.
"I deserve it after this match," Federer said. "That's how I feel."
Kokkinakis became the lowest-ranked man to beat a No. 1 player since No. 178 Francisco Clavet upset Lleyton Hewitt in 2003. That match was also at Key Biscayne.
Federer now has a losing streak after a career-best 17-0 start to the year. The match was his first since he lost to Juan Martin del Potro in the Indian Wells final Sunday, a match that also came down to a winner-take-all tiebreaker.
Did the losses have anything in common?
"Yes, 7-6 in the third," Federer said. "Other than that, not much."
Kokkinakis, 21, has long been regarded as a promising talent thanks to a thunderous serve and forehand, but has been plagued by injuries. The match was his first against Federer, although they've practiced together.
"I've always liked his game," Federer said. "I'm happy for him that on the big stage he was able to show it. It's a big result for him in his career, and I hope it's going to launch him."
Federer's defeat left both No. 1 players out of the tournament. Simona Halep lost hours earlier to Agnieszka Radwanska 3-6, 6-2, 6-3. Eight-time women's champion Serena Williams was eliminated Wednesday.
Federer won't be playing to reclaim the No. 1 spot anytime soon. He said he'll skip the upcoming clay season for the second year in a row, including the French Open.
In other men's play, American Frances Tiafoe broke serve only once-after he was two points from defeat-and that was enough to rally past No. 21-seeded Kyle Edmund 7-6 (4), 4-6, 7-6 (5). No. 4 Alexander Zverev edged Daniil Medvedev 6-4, 1-6, 7-6 (5).
Federer's match turned when he played a poor service game and was broken at love to fall behind 3-1 in the second set. Kokkinakis never broke again but held the rest of the way, consistently topping 125 mph with his serve.
"Every time I had chances, something bad happened," Federer said. "Wrong decision-making by me, good decision-making by him. It's disappointing. I don't know why I couldn't get to any level I was happy with today."
Federer kept one exchange going by hitting a volley behind his back, but couldn't win even that point. He laughed then-it was early in the match-but looked grim two hours later as the end neared.
On match point, Federer buried a backhand return in the bottom of the net. Kokkinakis screamed in celebration, waved his index finger and gestured for more noise from the appreciative capacity crowd.
"It's pretty crazy," Kokkinakis said. "I'm pretty happy about it."
The match was the last at Key Biscayne for Federer, a three-time champion. The event is moving next year to the Miami Dolphins' stadium.
Nadal will become the new No. 1 even though he missed Key Biscayne because of a hip injury that also forced him to skip Indian
Wells.