World No 1 Novak Djokovic has called tennis star Maria Sharapova a 'great fighter' following her retirement. 

The 32 year-old Russian announced her retirement this week following a stellar career. The former World 1 beat Serena Williams at Wimbledon in 2004 when she was just 17 years-old. And since then she has won five Grand Slam titles and a silver medal in the 2012 Olympic Games. 

And Djokovic who heard about her retirement after he booked a spot in the quarter-finals at the Dubai Duty Free Tennis Championships encouraged the crowd to applaud the Russian to mark her achievements. 

He said: "I'm sorry that it had to end with an injury obviously but at the same time she had a fantastic career and she can be proud of herself.

"She's great fighter. As dedicated as someone can really be in our sport.

"The willpower and the willingness to kind of overcome all the obstacles she had, especially ... with injuries and surgeries and trying to fight back, come back to the court and play on her desired level.

"It's truly inspirational to see what mind of a champion she has. I'm sorry that it had to end with an injury obviously but at the same time she had a fantastic career and she can be proud of herself."