The plan for Nadal was to return on Thursday in an exhibition tournament in Abu Dhabi after missing seven months of play with tendinitis in his left knee. Nadal wrote on his Facebook page on Tuesday that he was forced to pull out of the tournament on orders from his doctors, who said he needed to give his body rest due to a fever.
"My rehab has gone well, my knee feels good and I was looking forward to competing," Nadal said, according to the Associated Press.
Nadal last played in June at Wimbledon, where he was upset by 100th-ranked Lukas Rosol of the Czech Republic in the second round, losing 7-6 (9), 4-6, 4-6, 6-2, 4-6 for his earliest exit from the tournament since 2005.
"Rafael Nadal has been forced to make a last-minute withdrawal from the 2012 event due to a stomach virus," organizers said in a statement released on Tuesday, according to the Guardian. "Nadal, who has competed in all four previous tournaments, was advised by doctors not to travel or compete due to the illness."
Nadal previously won the tournament in Abu Dhabi in 2010 and 2011. He is scheduled to play in his first ATP event since the injury, the Qatar Open, starting on New Year's Eve, but the new stomach virus may keep him out of that as well.
The knee injury kept Nadal from defending his Olympic singles gold medal from Beijing in 2008 after he was forced to pull out of the London Olympics, where he was set to be Spain's flag-bearer. He also missed the U.S. Open as well as Spain's Davis Cup final against the Czech Republic. Without Nadal, Spain was unable to defend its title and lost the Cup.
Nadal is currently ranked fourth in the world, his lowest ranking since 2010, according to SI.com, after missing time with knee issues, but expressed no concern about his rank a few months ago and that his focus is on getting healthy and winning majors and that his ranking is not the most important concern.
"At this point of my career (the ranking) is not the most important thing," Nadal, told Efe, according to ESPN.com. "Now the most important thing is to make a good recovery and right now my knee is not ready to compete in a Grand Slam; I'm going to try to recover as soon as possible to come back feeling strong, sure that I can compete and train the best that I know how."
Top-ranked Novak Djokovic and No. 3 Andy Murray are scheduled to play at Abu Dhabi.
Nadal said last week that he was nervous about returning from his injury, but that he has trust in his doctors and his training team with helping him to return to top-form.
"I have my doubts. It's normal. We are talking about a knee, so of course I am afraid to see how it is going respond," Nadal told Canal Plus television last Friday. "But I can only trust my doctors and believe in myself and that everything will be all right."
Nadal's style of play is one reason why he has been so dominant during his career, but it is also the main reason why he has dealt with knee injuries multiple times. He plays aggressively from behind the baseline and relies on powerful strokes and speed to counter opponent's attacks.
Nadal's knees don't take as much of a beating on clay courts, but are more susceptible to injury on the hard courts that are common on the ATP tour. The 26-year-old Spaniard said he may skip more events early in the year and will play more clay matches in the future and avoid hard courts to help with his knees.
"I'm prepared to accept that at the start my knee might not respond well and I may have to take it easy, mixing periods of play and rest for the first three months," Nadal said.
The 11-time Grand Slam champion will likely return for the Australian Open and Nadal also confirmed earlier this year that he will participate in the Mexican Open tournament, which takes place in early 2013 after the first Grand Slam of the season. The Australian open is set to begin on Jan 14, while the clay-court Mexican Open is scheduled for Feb. 25-March 2.
"His training has gone well, physically and mentally he is in good shape," Toni Nadal said. "We can't put a fixed date down yet for his return. But all signs are positive that he will return sooner than later."
The 11-time Grand Slam champion had hoped to return before the 2012 season ended, but the sickness made that an impossibility. Nadal is hoping to be fully healthy by April, when he will play at Monte Carlo, a clay-court tournament he has dominated for eight consecutive years.
Nadal is considered to be one of the best players in the world and the greatest clay court player of all-time. He has won seven French Open titles, two Wimbleldon's and one U.S. and Australian Open title. Nadal has gone 42-6 this year and has won four singles titles, including the French Open for his 11th career Grand Slam victory.