France, Jan. 30 -- Novak Djokovic says he hopes to return to action in a month's time but is "not sure" how quickly his injured hamstring will heal. Roger Federer has been among those hailing Djokovic's "incredible effort" in winning a 10th Australian Open and a record-equalling 22nd Grand Slam title on Sunday.

"Incredible effort, again! Many congratulations," the retired Federer, who won 20 majors, wrote in a brief message on Instagram.

Djokovic defeated Stefanos Tsitsipas in straight sets earlier Sunday to add another Australian Open trophy to his seven at Wimbledon, three at the US Open and two from the French Open.

His collection of 22 Grand Slam titles takes him level with Rafael Nadal.

Djokovic at 35 is one year younger than Nad...