Melbourne - A unusually long list of injuries and illnesses could take its toll on the Australian Open, which has already seen withdrawals by Serena Williams and Andy Murray.
A rundown of who has been struggling in the lead-up to the first Grand Slam of the year:
Six-time Melbourne champion has been sidelined since Wimbledon in July with a right elbow injury, although the Serb intends to play exhibitions this week and insists he "is ready".
A knee injury forced the Spanish world number one out of the warm-up Brisbane International, but he has arrived in Melbourne and expected to be a leading contender.
The 2014 champion is returning after two operations on a knee cartilage injury. Pulled out of Abu Dhabi exhibition appearance late last month.
Calf and wrist problems kept the tall Canadian out of action since last October. Played the Brisbane International, but was bundled out by a wildcard.
Leg was strapped at the Brisbane event which he said related to fluid on the back of his left knee. It didn't seem to trouble Australia's big hope, who won the tournament.
The American retired from a match at the Hopman Cup with an injured hip, but returned two days later when he lost to Roger Federer.
The Austrian world number five pulled out of the warm-up Qatar Open just hours before his semi-final with flu and a fever.
The 2008 Australian Open runner-up withdrew from the Qatar Open before it started with a wrist injury.
World number three retired from Brisbane after collapsing with severe leg cramps. She is playing the Sydney International this week.
The US Open champion withdrew from Brisbane to rest a troublesome knee and was knocked out of Sydney in the first round. Had a remarkable 2017 after almost a year out with a left foot injury.
A semi-finalist in Melbourne two years ago, the Briton's Brisbane campaign ended early when she retired with a right hip injury.
The rising French star retired in tears from Brisbane with a back injury in the opening round, saying she could barely move.
The two-time Wimbledon champion pulled out of Brisbane with a viral illness. She missed last year's Australian Open after being attacked with a knife near her Czech home.
The German, ranked 12, withdrew from the Sydney International just hours after beating Caroline Wozniacki to win the Auckland Classic on Sunday, citing a right knee injury.