Tennis-Top seed Murray knocked out in Australian Open fourth round

MELBOURNE, Jan 22 (Reuters) - Top seeded Briton Andy Murray was knocked out of the Australian Open in the fourth round on Sunday, losing 7-5 5-7 6-2 6-4 to German world number 50 Mischa Zverev on Rod Laver Arena. Murray's defeat follows that of reigning champion Novak Djokovic, who fell to Denis Istomin in the second round on Thursday, leaving the men's draw at the year's first grand slam without its top two seeds at the quarter-final stage. (Reporting by Nick Mulvenney, editing by Peter Rutherford)