Sofia Kenin insisted her leg injury was improving as she prepares for her Australian Open title defence.

In a rematch of last year's Australian Open decider, Kenin was crushed 6-2 6-2 by Garbine Muguruza in the Yarra Valley Classic quarter-finals on Friday.

Kenin, 22, said she struggled with a leg injury which she hopes will not affect her at Melbourne Park, where the year's first grand slam begins on Monday.

"It was my left groin and my left glute, it was completely sore," the American told a news conference on Saturday.

"I think I was rolling a lot yesterday. Even before the match I rolled probably like an hour before they even finished. I was just rolling with the Theragun. It kind of got better, but it wasn't the best. She obviously played well."

Kenin, who will face Maddison Inglis in the Australian Open first round, added: "It's better, which I don't understand. From a match, now today it's better. Thank God. Obviously I'm not going to complain about that. I want it to be better for AO."

The defending champion's injury worry is just the latest ahead of the Australian Open, with Serena Williams, Naomi Osaka and Victoria Azarenka among those withdrawing from lead-up tournaments.

Kenin believes quarantine ahead of events had an impact, as well as long lay-offs.

"People who haven't played matches for two weeks, it's obviously not the same. Everyone is using this tournament to prepare for Australian Open," she said.

"Obviously you can see that being in a room for two weeks, not playing, practising, it's not the same as playing a match clearly. After two matches, my leg is completely sore. 

"Yeah, it's obviously different. But everyone's obviously going to be ready for Australian Open, for sure."