Kei Nishikori has withdrawn from next month's Australian Open and the inaugural ATP Cup as he continues to recover from elbow surgery.
The world number 13 went under the knife in October and has not played since his third-round exit at the US Open in August.
Nishikori was due to represent Japan in the ATP Cup in Perth but follows Yoshihito Nishioka in withdrawing from the team.
"Unfortunately I have to pull out of the ATP Cup and the Aussie Open," Nishikori said in a statement on his 30th birthday. "Today, together with my team, we have made this decision as I am still not 100 per cent ready/healthy to compete at the highest level.
"This decision was not taken lightly as Australia is one of my favourite places to compete. Together with my team I will keep working hard to be back on court as soon as possible. Thanks for all the support."
Nishikori reached the Australian Open quarter-finals for the fourth time in 2019 after winning the Brisbane International.
The former world number four and 2014 US Open runner-up also recorded quarter-final appearances at the French Open and Wimbledon this year.