Novak Djokovic’s Serbian teammates admit they aren’t sure if the world No.1 will contest the Australian Open after his late withdrawal from the ATP Cup.

Djokovic is bidding for a men’s record 21st grand slam title and a 10th Australian Open crown.

The 34-year-old is on the entry list but yet to commit to the Australian Open following the COVID-19 vaccination mandate agreed by Tennis Australia and the Victorian Department of Health.

Djokovic has repeatedly declined to disclose whether or not he is vaccinated, citing privacy concerns.

His involvement at the Open has further been clouded by the world No.1 withdrawing from the Serbian team taking part at the ATP Cup from January 1 in Sydney.

World No.33 Dusan Lajovic was the late call-up to replace the 20-time grand slam winner as Serbia’s No.1 at the teams event in Sydney and did his best to explain the situation on Thursday.

“He kept in touch with all of us and it was a last-minute decision, the Australian Open is still uncertain, I don’t know the information,” he said.

“I think that will come in the next couple of days or whenever is the deadline.

“We don’t know right now, but hopefully he’ll be there and be able to play the grand slam.”

Lajovic said Djokovic had not disclosed his reasons for skipping Serbia’s defence of the ATP Cup.

“He said I’m not coming to the ATP Cup, we’ll see about the Australian Open,” he said.

“He didn’t specify if he’s coming or not, (but) that he’s waiting for a decision.”

Fellow 20-time grand slam winner Roger Federer (knee) has already confirmed he’ll miss the tournament, while Rafael Nadal is recovering from COVID-19 as he too eyes a record 21st major title.

– AAP