Nadal, Djokovic under Wimbledon cloud as Federer waits to

Rafael Nadal and Novak Djokovic enter Wimbledon plagued by injury fears and self-doubt, leaving Roger Federer convinced that this could be a golden opportunity to capture a record eighth title.
World number one Nadal, fresh from a record ninth French Open, was Wimbledon champion in 2008 and 2010 and runner-up in 2006, 2007 and 2010.
But his last two visits have been humiliating disasters.
The Spaniard suffered his first-ever opening round exit at a Grand Slam in 2013 to Belgian journeyman Steve Darcis, who was ranked 135 and has not won a main tour match since.
Twelve months earlier, the world's 100th best player, big-hitting Lukas Rosol, put him out in the second round, a defeat which precipitated a seven-month absence from the sport for the man from Mallorca.

Rosol could be a second round opponent this year.

The 28-year-old Nadal hinted at another Wimbledon letdown in the immediate aftermath of his triumph over Djokovic in the French Open final two weeks ago, when he claimed his 14th major, and this weekend hinted at more trouble to come.
"I've said before this is really the most dangerous tournament of the year," said Nadal, who has been seeded second despite his world number one status.
"When I arrive at Roland Garros I have already played for one month on clay. I played a lot of matches. So more or less I can imagine how I am going to play.

"Here, especially the beginning of the tournament, the courts are a little bit faster. The feeling on court is a little bit strange for everybody. The match is decided in a few balls, so you need to convert the small opportunities that you have."
Nadal, who faces Slovakia's Martin Klizan in the first round, suffered an opening exit on grass at Halle last week, a straight-sets defeat by German world number 85 Dustin Brown.
World number two Djokovic, who won his only Wimbledon title in 2011 and was runner-up to Andy Murray in 2013, has not played a grasscourt warm-up event since 2010.

The 27-year-old Serb won the last of his six majors at the Australian Open in 2013 and his latest thwarted attempt to win a first French Open represented his seventh defeat in 13 finals at the majors.