Novak Djokovic begins Australian Open title defence with unconvincing victory vs Jan-Lennard Struff

Reigning champion Novak Djokovic was forced to dig deep to overcome the challenge of Jan-Lennard Struff to reach the Australian Open second round.

The Serbian was perhaps surprised to find himself forced into a first-set tiebreak having been 5-2 up but scraped past Struff.

From there, it looked like plain sailing for the world number two until he suffered a third-set meltdown to invite Struff back into the contest, before eventually battling past the spirited German to seal a 7-6, 6-2, 2-6, 6-1 victory in two hours and 22 minutes at the Rod Laver Arena.

Having played Struff on a number of occasions in his career, Djokovic would have known not to take the 29-year-old lightly.

But even at 5-2 up and looking largely comfortable, the 32-year-old would have been surprised by his opponent's valiant fightback.

Struff broke back after a series of uncharacteristic errors from Djokovic and took it to a tiebreak, forcing the seven-time winner all the way before narrowing missing out as Djokovic wrapped it up 7-5.

Keen to avoid a repeat of the first set, Djokovic stormed out of the blocks in the second set, needing just 27 minutes to take a two-set lead at 6-2.

Some of the shots that Djokovic was producing had the crowd on their feet as an unusual variety of aggressive shots showcased some of his finest work, especially with a flick of the forehand to take two set points.

As Struff plotted his comeback, the third set was a whole lot closer and Djokovic had to fight back from an early break to level at 2-2 before a series of errors cost him a second break at 4-2.

And that would prove costly as the second seed soon found himself struggling to contain his frustration as he handed the third set 6-2 on a plate to Struff, who was more than happy to oblige.

Djokovic regrouped in the fourth set, taking an early break and this time held his nerve as he went on to secure victory - but there will be questions about his implosion in the third set and whether he would survive such an episode against a higher-ranked opponent.