PERTH, Australia (AFP) —Roger Federer took another impressive step towards his Australian Open title defence yesterday with a straight-sets win over Russian Karen Khachanov at the mixed teams Hopman Cup, as many of his main rivals faltered due to injury.

Around the time Federer was warming up for his match with the 45th-ranked Russian, Andy Murray announced he was pulling out of the Brisbane International, while Novak Djokovic a few days earlier withdrew from his season opener in Abu Dhabi.

Rafael Nadal, Stan Wawrinka, Milos Raonic and Kei Nishikori are also under injury clouds, while world number eight Jack Sock succumbed to a hip problem earlier in the day in Perth, forcing him to retire from his singles match.

But there were no such dramas for the elder statesman Federer, who 12 months ago stunned the tennis world by ending an almost four-year Grand Slam drought with a victory at the Australian Open, after also preparing at the Hopman Cup.

The 36-year-old was too good for Khachanov, making it two straight-sets wins from as many singles matches this week as Switzerland beat Russia 3-0 in their Group B tie in front of a record Hopman Cup crowd.

Federer was stretched by Khachanov, particularly in the second set when the pair traded powerful groundstrokes.

The Russian held a set point in the tie breaker and also saved two match points held by Federer, before the Swiss champion prevailed after Khachanov hit a forehand perilously close to the line.

It was called in by the linesman, but Federer challenged and was rewarded when replays showed the ball was out by millimetres, handing the 19-time Grand Slam champion a 6-3, 7-6 (10/8) win.

The 74th-ranked Belinda Bencic, on the comeback trail after injuries stalled her promising career, then upset world number 15 Anastasia Pavlyuchenkova in three sets, 6-1, 3-6, 6-3 in just under two hours to clinch the tie for the Swiss.

In the dead mixed doubles rubber, the Swiss completed a clean sweep with a three-set win under the Fast4 format.

Both Switzerland and the United States’ pairing of Sock and CoCo Vandeweghe, who beat Japan 2-1 in contentious circumstances earlier in the day, have won their opening two ties.

The victor in their clash tomorrow will advance to Saturday’s final, and Federer said he expected Sock to be fit for that tie.

Sock retired early in the second set of his men’s singles clash with Japan’s Yuichi Sugita, having injured his hip during a first-set tie-breaker.