Even the first round could be tricky for Federer, who will face a player he's never beaten as he begins his bid for a sixth straight Wimbledon title. He'll open against Dominik Hrbaty -- a 30-year-old Slovakian playing in his 45th consecutive major -- in the first match on Centre Court on Monday.
In the women's draw Friday, top-seeded Ana Ivanovic and two-time champion Serena Williams are in the same top half. No. 2 Jelena Jankovic and Venus Williams, the defending champion and four-time winner, are in the bottom section.
Hrbaty beat Federer in their only two previous matches in 2000 and 2004, but has slid from No. 12 in the rankings to No. 272 since their last meeting.
If he gets past Hrbaty, Federer could face a third-round match against rising French star Gael Monfils, whom he beat in the French Open semifinals, and either 2002 champion Lleyton Hewitt or Fernando Gonzalez in the fourth. Federer's projected quarterfinal opponent is Spain's fifth-seeded David Ferrer.
Djokovic, ranked No. 3, beat Federer in the Australian Open semifinals to end the Swiss star's winning streak there. Djokovic has the size, power and overall game to challenge Federer's supremacy.
Djokovic believes Federer is vulnerable after his lopsided defeat to Nadal in the French Open final and lack of a Grand Slam title this year.
"Some things are changing. I think he's a little bit shaken with that loss and mentally he has been struggling in the last couple of months," Djokovic said this week in London. "New names are coming, fresh talented players who believe more they can win against him and I am one of them. Suddenly he is worried a little bit."
Few players have a winning record against Federer. Nadal, at 11-6, is the only one to have done it consistently.
Federer and Nadal each won grass court titles last week. Nadal beat Djokovic at Queen's Club to claim his first title on the surface, and Federer extended his grass-court streak to 59 matches at Halle in winning his 10th grass-court title. The previous four times Federer won at Halle, he won Wimbledon three weeks later.
"That's exactly what I hope for this time," Federer said. "That's why I'm so satisfied. That's why I will go to Wimbledon with a lot of hope."
Nadal, coming off his fourth straight French Open victory, will open against German qualifier Andreas Beck. Nadal could face Mikhail Youzhny in the fourth round, Britain's Andy Murray or 2007 semifinalist Richard Gasquet in the quarterfinals and No. 4 Nikolay Davydenko or No. 6 Roddick in the semis.
Roddick has a possible fourth-round encounter against fellow American James Blake.
Djokovic has a first-round match against Michael Berrer of Germany and could face a tough second-round matchup with Russia's Marat Safin, a former No. 1 and two-time Grand Slam winner. Djokovic could meet 2002 finalist David Nalbandian in the quarterfinals before a potential showdown with Federer.
Venus Williams, seeded No. 7, will open defense of the women's title against British wild card Naomi Cavaday. Williams could meet Sania Mirza in the third round, Daniela Hantuchova in the fourth, Jankovic in the quarters and 2004 champion Maria Sharapova in the semifinals.
The Williams sisters could meet in the final again.
Ivanovic, who took over the No. 1 ranking after winning the French Open for her first major title, faces Rossana De Los Rio of Paraguay in the first round. She could face Anna Chakvetadze in the quarterfinals and Serena Williams or No. 4 Svetlana Kuznetzova in the semis