Serena Williams's coach Patrick Mouratoglou has tipped her to challenge for all four Grand Slam titles this year.
The Frenchman believes that the 32-year-old is capable of pulling off a clean sweep in 2014, a feat that has not been achieved since Steffi Graf managed it in 1988.
"She's beaten all the top players many times, so you can aim that high," Mouratoglou told BBC Sport.
"Of course it would be exceptional because it's crazy to do that. It's happened just a few times in the history of tennis - but she can do it and the goal is to do the best possible in all four Grand Slams. So why not?"
The first Grand Slam of 2014, the Australian Open, gets underway on January 13.
