US Open champion Marin Cilic of Croatia has withdrawn from this month's Australian Open with a shoulder injury.
The world number nine, 26, has been struggling with the injury for more than a month and misses the Grand Slam in Melbourne on the advice of doctors.
"I have a right shoulder injury which has hampered me for some time now," said Cilic.
His absence has guaranteed Great Britain's James Ward a place in the first Grand Slam of the season.
Ward was sixth reserve for the tournament, which starts on 19 January, when the entry list was published at the end of last season, but has benefited from the withdrawal of others.
It means the 27-year-old, who has risen to 101 in the world rankings, will not need to line up alongside compatriots Kyle Edmund and Liam Broady in this week's qualifying event.
"I am really sad that I won't be able to participate in Melbourne, especially after winning the last Grand Slam in New York," said Cilic, who beat Kei Nishikori to win his first Grand Slam title last September.
"But I was advised by doctors to be careful as much as possible to avoid even more serious problems.
"It is improving day by day, but I still don't feel fit enough to be able to compete at the highest level."
Cilic reached the semi-finals of the Australian Open in 2010 and is also a Wimbledon quarter-finalist. He has won 13 ATP singles titles.
Earlier in the week, world number 12 Jo-Wilfried Tsonga pulled out with an arm injury.