Johanna Konta overcame a tough start to defeat Ajla Tomljanovic and advance to the quarter-finals of the Brisbane International.

For the second match running Konta fought back from losing the first set, eventually triumphing 4-6, 6-1, 6-4.

Konta, fresh from a tough first‑round encounter with Madison Keys, struggled to find the same rhythm at the start and had difficulty protecting her usually dominant serve.

Tomljanovic broke Konta’s serve four times, meaning when she held for just the second time herself it was enough to take the first set. But then Konta kicked in to gear, finding her range on serve while still causing damage on her opponent’s, and won the second set 6-1.

Konta was having a comfortable time of it in the final set until a late rally from the Croatian, but the British No1 eventually served it out at the second attempt to set up a last-eight match against Elina Svitolina or Ana Konjuh.

Konta said on BT Sport: “It was a tough match, she played incredibly freely. There wasn’t a lot in it but I am very happy to get through that. I didn’t start off the way I wanted to. She played very well. I am taking it one match at a time, every match is a battle and I am sure the next one will be.”

The top seed, Garbiñe Muguruza, was forced to retire injured during her second-round match at the Brisbane International as Aleksandra Krunic advanced. The 2017 Wimbledon champion endured muscle cramps when she was 5-2 up in the third set with the first two sets shared and pulled out, setting the Serbian Krunic up for a quarter-final clash with seventh seed Anastasija Sevastova, who defeated Sorana Cirstea.

Meanwhile, in Perth, Roger Federer continued preparation for his Australian Open title defence with a 6-3, 7-6 (8) win against Karen Khachanov at the Hopman Cup, giving Switzerland a 1-0 lead over Russia. The 36-year-old Federer had his service broken by the 21-year-old Khachanov in the opening game, but rebounded to break back immediately and won the opening set in 29 minutes.

Khachanov matched Federer impressively with backhand winners in the second set before a back-and-forth tiebreaker. Federer saved a set point in the tiebreaker and won on his third match point after a successful challenge.

“I had to work hard, experience helps sometimes,” said Federer, who defeated Rafael Nadal in the Australian Open final last year. “It’s good to be free-swinging and young, like he is. I remember those days …”

Earlier, the United States beat Japan 2-1 after an illness withdrawal by one of the Japanese players. But the win may come at a cost after Jack Sock injured his hip. The Hopman Cup has a contingency plan should Sock not be fit to play Federer on Thursday.