Federer hasn't reached the semifinals since 2006, and for the first time in five years he's not seeded No. 1 for the tournament beginning Wednesday. Nemesis Rafael Nadal is top-seeded, and five-time champion Serena Williams is No. 1 on the women's side.
The focus in recent months has been on Federer's decline in major events, but the slippage has been even more pronounced in Masters tournaments - the ATP Tour's most prestigious and lucrative events aside from the Grand Slams.
Federer won his most recent Masters title at Cincinnati in August 2007.
"I hope this year I can change that a bit and get on a good roll again, because I've done so well over the last few years that I'd like to win a few again,'' Federer said.
His 14 Masters titles rank second only to Andre Agassi's 17, while Nadal has 13. But Federer has come up short at 12 Masters tournaments in a row, losing three finals, including two against Nadal.
Federer's most recent Masters setback was last week in Indian Wells. Returning from a six-week layoff due to a back injury, he reached the semifinals before losing to Andy Murray.
"You're just like disappointed a bit, but it was a decent tournament,'' Federer said. "Not the greatest of all time, but it was all right. Hopefully I'll play well in Miami.''
Nadal is seeking his first Key Biscayne title. He ended Federer's 4 1/2-year reign atop the rankings last August and won his latest title Sunday at Indian Wells, then was on a plane that night to Miami.
"The good thing of tennis is when you lose you have another chance next week,'' Nadal said. "The bad thing is when you win, most of the time you don't have enough time to enjoy the victories.''
Nadal actually has a few days this week to savor the achievement. Seeded players at Key Biscayne receive first-round byes, and the Spaniard will play his opening match Saturday night.
Federer is seeded second, and 2007 champion Novak Djokovic is third. Seeded fourth is the improving Murray, who has beaten Federer four times in a row. Andy Roddick is fifth.
Federer, Djokovic and Roddick are in the same half of draw. The only top player missing from the 96-man field is defending champion Nikolay Davydenko, sidelined by a foot infection.
The only top woman absent will be Maria Sharapova, whose ranking has slipped to No. 30 as she recovers from shoulder surgery last fall.
Williams seeks her third consecutive Key Biscayne championship. Last year, when she tied Steffi Graf's record of five titles in the event, Williams dubbed the it "The Serena and Steffi Open.''
Three-time champion Venus Williams is seeded fifth and could meet her younger sister in the semifinals. Dinara Safina is seeded second and Jelena Jankovic third, with the top 10 women all competing.
Federer won Key Biscayne in 2005 and 2006, when he was winning almost everything, but he played a dismal third set in the quarterfinals last year and lost to Roddick. The defeat was part of a yearlong slump for Federer interrupted only when he won the U.S. Open for his 13th Grand Slam title, one shy of Pete Sampras' record.
Federer has lost five consecutive matches against Nadal, most recently last month in the Australian Open final. While Nadal's lead in the rankings is widening, Federer still considers the gap small.
"I don't know if I really have to like make a major jump,'' Federer said. "With Rafa the last few matches, for instance, it has been down to a few points here and there. That makes a difference of winning a Slam or not winning a Slam. So I think I just have to make sure next time I play him I get those couple of points.''
The latest loss against Nadal left Federer sobbing during the trophy ceremony. Federer later said he was embarrassed because the tears were misinterpreted.
"It had nothing to do with, 'Oh my God, I'm never going to win this tournament again,''' he said. "We care about this game and try hard. When it doesn't happen, you know, we're not happy, we're sad. ...
"Instead of getting it out maybe in the locker room, it happened in the center court in front of anybody. That's the tough part for me to handle. But I could handle it, and I still believe it shows that there is a human side to any player.''