WASHINGTON, March 25 (Xinhua) -- World number one Roger Federer revealed that he will opt out of the upcoming clay-court season after he lost to Australian qualifier Thanasi Kokkinakis in the second round of the Miami Open on Saturday.

"Yeah, I decided not to play," Federer said of the clay-court season. "I didn't play great last week either. Nothing new, in my opinion. I'm trying to figure things out, so I have time now."

"I'm a positive thinker. I feel like every match is another opportunity. Especially after losing one, clearly I'm down right now. I'm disappointed. I'm frustrated a little bit that I couldn't find a way. It's unfortunate how it goes."

The loss prompted the announcement that, for the second consecutive year, he would skip the clay-court season, including Roland Garros. It proved a masterstroke in 2017 as he went on to claim a record eighth Wimbledon title.

Federer, 36, knows that it is as much about keeping a spark of motivation alive as it is about managing his body.

"It's pretty simple at the end of the day. You go back to the practice court or go on vacation, you really take a break, get away from it all. When you come back to the practice court to work, whatever it is, you do it at 100 per cent."

The 21-year-old Australian's 3-6, 6-3, 7-6(4) victory drew high praise from the Swiss. This was an opponent Federer had spent time training with at his Dubai base.

"He's a cool guy, a cool demeanour," Federer said. "He's been to Dubai to practise with me a couple of times. I knew him very well. We have worked very hard together. I've always liked his game.

"I'm happy for him that on the big stage he was able to show it, centre court, Miami, people watching, beating me. It's a big result for him in his career. I hope it's going to launch him, really getting his ranking up."