Speaking Thursday on the eve of his opening match at the Sony Open, Federer said he's already contemplating what to wear for the 2015 U.S. Open.
"It's kind of hard sometimes to put myself in the right mindset to know, am I going to like stripes in one and a half years?" said Federer, with a smile. "I'm not sure, you know? Right now I maybe do, but in one and a half years, it's maybe not so cool."
Federer, a 17-time Grand Slam champion, wants to play well and look good. He has a popular line of tennis apparel, and Vogue editor-in-chief Wintour often sits in his box at Grand Slam tournaments.
He's won the tournament near Miami twice, in 2005 and '06. Federer said he's learned a lot about fashion during his career.
"My advice probably is you've got to make sure you wear the clothes and not the clothes wear you," he said. "Don't wear something you totally feel uncomfortable with, but take some chances. Play around a bit.
"I felt very uncomfortable in suits when I was younger. So what I just started doing was wearing suits when I was going to dinner. I used to overdress a little bit, so I got used to wearing suits. Now wearing a suit is like wearing a track suit for me."