With the Australian Open on the horizon, there are again doubts over the fitness of a number of the top players in the men's draw.

As Novak Djokovic and Andy Murray struggled for fitness in 2017, Roger Federer and Rafael Nadal took full advantage by winning two grand slams apiece.

But what condition are the ATP's premier players in going into the first slam of 2018? Here we break down how things are shaping up for the usual suspects at major tournaments.

Rafael Nadal 

The world number one withdrew from the ATP Finals with a knee injury and the issue appears to still be causing him problems. He withdrew from the Mubadala World Tennis Championship to limit his schedule and then pulled out of the Brisbane International, meaning he will head to Melbourne without having played a warm-up match.

Novak Djokovic

Djokovic has not played since his Wimbledon quarter-final defeat to Tomas Berdych and, after undergoing surgery on his right elbow, it seems he still has strides to make in his recovery. The 12-time grand slam champion withdrew from the Mubadala exhibition event on Friday and looks a serious doubt to even participate at the Australian Open.

Andy Murray

Like Djokovic, the last eight of Wimbledon is the last time Murray graced a competitive court, a hip issue cutting his 2017 season short. There have been reports he is behind schedule in his recovery but Murray did play a practice match in Abu Dhabi against Roberto Bautista Agut in place of the injured Djokovic, losing the one-set clash 6-2. 

Stan Wawrinka

The most prolific interrupter of the big four's dominance of the grand slam circuit, Wawrinka missed the US Open because of a knee injury and delayed his return by pulling out of Mubadala. However, the Swiss has vowed to play in Melbourne even if he is not fully fit.

Roger Federer

While his rivals all struggle for fitness, Federer is already gearing up at the Hopman Cup. The seemingly ageless 19-time grand slam champion is the clear favourite to retain the title in Melbourne.