As a result of the defeat on Saturday, Federer, winner of a record 20 Grand Slam men's singles titles and the current world No. 1, will cede the top spot to Spanish arch-rival Rafael Nadal when the new rankings are released on April 2, reports Efe.
After the match, the 36-year-old Federer said he had decided to skip the entire clay-court season, including the French Open, for the second straight year.
Federer, who needed to reach the quarter-finals of the Miami Open -- an ATP World Tour Masters 1000 hard-court event -- to maintain his No. 1 ranking, seemed on course for a routine victory when he won the first set in 35 minutes on the strength of one service break.
But the 21-year-old Australian qualifier, a highly touted prospect who has suffered injury setbacks and is currently ranked No. 175, came back strongly in the second set.
After saving an early break point, Kokkinakis broke Federer's serve for the first time in the fourth game and then consolidated that break to grab a 4-1 lead.
The third set dragged out much longer than Federer would have liked after he failed to convert a pair of break point opportunities in the sixth game.
The contest came down to a tiebreaker, which was closely contested but eventually won by Kokkinakis when Federer dumped a backhand return into the net on match point.
"This is nuts," Kokkinakis was quoted as saying afterward on the ATP World Tour's website. "It's an unreal week for me. I've trained with (Federer) a bunch of times and he's a great role model for the sport, but I took what I learned and played my game and executed."
The loss was a rare early round loss for the Swiss legend, who has played some of the best tennis of his career since returning from an injury hiatus 14 months ago.
His decision to skip the clay-court season once again is unsurprising, especially considering that the move paid off last year when he dominated the ensuing grass-court season and captured a record eighth Wimbledon title last July.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
