News of Roger Federer's knee surgery caught Novak Djokovic by surprise and the world number one said he hoped to see his Swiss rival back on court soon as the sport needs him. Federer said he would miss a number of tournaments, including the French Open in May, after undergoing keyhole surgery in Switzerland last week. Federer suffered a groin problem in his Australian Open quarter-final win against Tennys Sandgren and his movement appeared hampered in his defeat to eventual champion Djokovic in the semi-finals.