By Greg Stutchbury
MELBOURNE (Reuters) - Rafa Nadal's painful right knee will be tested on centre court on Wednesday when he meets German Tommy Haas in the second round of the Australian Open tennis.
The second-seeded Spaniard, who has been plagued with knee problems in recent years, said he had suffered a scare before the tournament began on Monday when he felt "unbelievable" pain in his right knee just from sitting in a chair.
The 10-times grand-slam winner, who has been hampered by injury in the last two Australian Opens and been knocked out in the quarter-finals both times, got treatment for his latest problem and easily advanced to his second-round clash with Haas.
The 33-year-old Haas last met Nadal at Melbourne Park in 2009, when the Spaniard was on his way to claiming his first, and so far only, Australian Open title.
Men's third seed Roger Federer will look to continue on his path to a potential semi-final meeting with his great rival when he plays Andreas Beck.
Women's champion Kim Clijsters will have an early start when she faces Stephanie Fortez Garcon in the second match on Rod Laver Arena, following China's Li Na, who will play Australia's Olivia Rogowska in the first match of the day.
World number one Caroline Wozniacki continues her quest to shake off the unwanted tag of holding the top rank without having won a grand slam, against Georgia's Anna Tatishvili.
Local fans will have plenty to keep them interested later on Rod Laver Arena when teenager Bernard Tomic, who came back from a two-set deficit to upset 2009 semi-finalist Fernando Verdasco in the first round, plays big-serving American Sam Querrey before Australian wildcard Casey Dellacqua meets third seed Victoria Azarenka of Belarus.
(Editing by Clare Fallon)