World number five Kei Nishikori is hopeful he will be fit for the Australian Open as he battles a hip injury.

The Japanese star hurt his hip flexor during a three-set loss to Grigor Dimitrov in the Brisbane International final.

Just a week out from the start of the year's first grand slam, the injury is a worry for the 2014 US Open runner-up.

But Nishikori, who pulled out of an exhibition event being played in Sydney, feels he just needs rest.

"I got injured during the match in the final. It's my hip flexor," he said. "It should be okay after a few days off. Hopefully I'll be ready for the Aussie Open next week."

Nishikori, considered a potential threat to win the title in Melbourne, has reached the quarter-finals at the tournament the past two years.