Australian Open defending champion retires for second straight year

Question

Rafael Nadal’s retirement against Andy Roddick in the quarter-finals of the 2010 Australian Open was the second straight year the defending champion withdrew from competition midway through their quarter-final match. Last year it was 2008 champion Novak Djokovic who controversially retired in his quarter-final against Andy Roddick due to heat exhaustion. No such controversy this time, but a little spooky nonetheless?