Roger Federer and Novak Djokovic [Source: Fox Sports Asia]

Novak Djokovic began his Australian Open title defence with a four-set win over Jan-Lennard Struff, while six-time champion Roger Federer claimed a comfortable victory at Melbourne Park.

World number two Djokovic overcame a third set wobble to beat Germany’s Struff 7-6 (7-5) 6-2 2-6 6-1.

Djokovic is a seven-time champion in Melbourne and is bidding for his 17th Grand Slam title overall.

Swiss Federer earlier breezed past American Steve Johnson 6-3 6-2 6-2.

It is the first time that Djokovic has dropped a set in the opening round of the Australian Open since 2006.

However, he saw off a tiring Struff in two hours 20 minutes for his 900th career win.

“Credit to him for fighting, he’s a very powerful player,” said Djokovic, who inspired Serbia to win the inaugural ATP Cup trophy earlier this month.

He faces either Japan’s Tatsuma Ito or Indian lucky loser Prajnesh Gunneswaran in the second round.

Denis Shapovalov, 20, lost his cool in a 6-3 6-7 (7-9) 6-1 7-6 (7-3) defeat by Hungary’s Marton Fucsovics.

The Canadian 13th seed was warned by the umpire for throwing his racquet down and responded: “I’m not breaking any rules.

“It’s my racquet I can do whatever the hell I want with it. What are you talking about, I didn’t break it.

“If I broke it, give me a code, 100%. I didn’t break my racquet. It was a terrible call, do your job.”

The rules state that players cannot “violently or with anger hit, kick or throw a racquet” within the tournament site.

Speaking after the match, Shapovalov admitted he had been nervous during the match but said the call from the umpire was “horrible”.

“I’m going to get fined for whatever the code was and he gets off the hook because he makes a call because he feels like it,” he said.

“I think it was a terrible call. The racquet was still intact and he gave me a warning because I did it two or three times.”