Roger Federer hailed Novak 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 a year younger than Nadal who was the defending champion in Melbourne.
Nadal was knocked out in the second round and is facing up to eight weeks on the sidelines with a hip injury.
Former world number one Federer retired last year at the age of 41 after failing to recover from a knee injury.
