Fifth-ranked Juan Martin del Potro will miss the Australian Open as he continues his recovery from a knee injury.

"I hope you have a great 2019. Recovery is going great and I will tell you later where I will be making my comeback," the 30-year-old Argentine wrote on Twitter.

"Unfortunately it won't happen in Australia ... but I'm happy with my progress."

The U.S. Open finalist fractured his right kneecap after a fall at the Shanghai Masters in October.

The Australian Open begins Jan. 14.