Novak Djokovic is 37 and was forced to stop playing because of an injury at two of the past four Grand Slam tournaments.

The 24-time Grand Slam champion Novak Djokovic has opted out of Serbia’s Davis Cup team after sustaining a muscular injury in his left thigh during the Australian Open.

Novak Djokovic has withdrawn from Serbia's Davis Cup tie against Denmark because of a hamstring injury. The 24-time Grand Slam champion was booed off court by some Australian Open fans last week when he retired with the issue after losing the first set of his semi-final against Alexander Zverev.

A week after a hamstring injury ended his run at the Australian Open, Novak Djokovic, 37, withdrew from Serbia's Davis Cup first-round qualifier, the country's tennis federation said on Tuesday, a move captain Viktor Troicki said has "weakened" the team.

Novak Djokovic was forced to retire hurt from the Australian Open semifinals - and the Serbian may not be back in action until the French Open.