World number one tennis star Novak Djokovic has admitted that he does not personally read all of the emails sent to him by the World Anti-Doping Agency.

Maria Sharapova faces a four-year ban from tennis after she admitted to failing a drug test after losing to Serena Williams at the Australian Open in January.

The Russian player tested positive for meldonium, which was added to the list of banned performance-enhancing substances at the start of 2016.

Sharapova admitted that she did not click on a link on December 22 from an email notifying her of the updated WADA list, and Djokovic has claimed that he mainly relies on his team to alert him to doping changes.

"I have to be frank that I don't read them all, but I have a team of people working with me and I have 100% faith and if there is any significant changes that I need to be aware of, then I am made aware of it," Djokovic told reporters.

"It's hard to judge and blame anybody here. I know this substance has been banned recently. It can happen to many people if it's only a case of negligence, of Maria and her team not paying attention to the change.

"Communication from the side of the governing bodies should be a bit better. We live very busy lives, there is a lot happening, the least we can do is have the double confirmation of the change from the ATP side."

Sharapova has denied reports that she was warned five times throughout December that meldonium was to be banned from January 1.