Kei Nishikori is pulling out of the Australian Open because his right wrist is not fully recovered enough from a torn tendon to withstand the rigor of best-of-five-set matches at a Grand Slam tournament.
Nishikori's agent, Olivier van Lindonk, announced the 2014 US Open runner-up's withdrawal in an email Wednesday.
The Australian Open, the first Grand Slam tournament of the new season, begins Jan. 15.
Nishikori has been sidelined since August because of his wrist. That kept him out of the U.S. Open, snapping a streak of appearing in 21 consecutive major tournaments.
Now he will miss his second major in a row.
"The Aussie Open is my favorite Slam," Nishikori said, via his agent.
Nishikori added: "My rehab is going well but I am just not ready 100 percent to come back yet in best of 5 set matches."
He is one of several top men dealing with injuries at the moment -- and he might not be the last to decide he can't play at the Australian Open.
Earlier Wednesday, Novak Djokovic posted a statement on his website saying he is still not sure whether he will enter the field at Melbourne, where he has won six of his 12 major championships.
Djokovic hasn't competed anywhere since July because of an injured right elbow. He will test his elbow at two exhibition events in Australia next week before figuring out whether to go to the Australian Open.
No. 1-ranked Rafael Nadal, the runner-up to Roger Federer at the Australian Open last year, withdrew from this week's Brisbane International tuneup tournament because of a bothersome right knee. Nadal won the French Open and US Open in 2017 to raise his major count to 16.
And three-time major champion Andy Murray also pulled out of the Brisbane International because of a bad hip and might opt to have surgery. Like Djokovic, he last competed at Wimbledon, nearly six months ago.
Nishikori, out nearly as long, has been a top-10 player and was the first man from Japan to reach a major final when he made it that far at the US Open in 2014, losing the title match to Marin Cilic.
Nishikori also reached the semifinals at Flushing Meadows in 2016.
He plans to return to competition at lower-tier Challenge events in Newport Beach, California, beginning Jan. 22, and at Dallas a week later.
The first ATP tournament on Nishikori's schedule as of now is next month's New York Open.