Marin Cilic ruled out of Brisbane International

The Croatian was due to play the first ATP Tour event of the 2015 season alongside a stellar cast including the likes of Roger Federer, Grigor Dimitrov and Kei Nishikori - the man Cilic defeated in the US Open final in September.

However, the 26-year-old is unable to feature and will be replaced by home favourite Marinko Matosevic at the Australian event.

"We're sorry to hear Marin Cilic has withdrawn due to medical reasons," read a post from the Brisbane International's official Twitter account.

"Aussie Marinko Matosevic now joins the field."

Cilic, the world number nine, recently spoke of his aim to break into the top five in the new year, after a fine 2014 that included his success at Flushing Meadows.

His withdrawal is now likely to raise concerns over his availability for the first grand slam of the season at the Australian Open, which starts on January 19.

"Very sad I had to withdraw from the Brisbane International tournament," Cilic wrote on Twitter. "At least happy for my friend Matosevic who got in instead of me."