Roger Federer won his match in the Hopman Cup with a 6-3 7-6 win over Karen Khachanov.
The world number two eased to a first set 6-3 win, but was pushed harder by the 21-year-old Russian in the second, when he squeezed through on a tie-break 7-6.
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Federer rode his luck in the deciding game to win 10-8 when Khachanov lost a review on a shot that went out of play.
Video - 'Oh what tennis!' - Federer wins super rally against Khachanov
Switzerland have their third game of the group against America on Friday.