Stefanos Tsitsipas was given a brief scare by lucky loser Zizou Bergs on Monday before roaring back to win his first-round match at the Australian Open 5-7, 6-1, 6-1, 6-3.

The Greek seventh seed, last year's runner-up in Melbourne, had been due to face 2021 Wimbledon finalist Matteo Berrettini but the Italian withdrew with an injury on the eve of the match.

If Tsitsipas had been expecting an easy ride against the 129th-ranked Belgian he was sorely mistaken, suffering the frustration of a costly service break in the 11th game to lose the opening set.

But the 25-year-old then found another gear and dropped just five more games in the rest of the match on a sun-baked Rod Laver Arena.

"Things were not as expected," he said. "I was expecting Matteo. Things like these are quite dangerous when you're preparing for many days in a row for a specific type of opponent."

But he said he was delighted with the level he reached and felt he was pushing Bergs "to the limit" in the final three sets.

"I'm glad things turned around," Tsitsipas added. "I'm glad I showed the fight and spirit that I usually show on court so it feels great."

Tsitsipas broke at his first opportunity in the second set to take a 2-0 lead, fending off three break points in total as Bergs battled hard in a set lasting 49 minutes.

He continued his momentum into the third set, breaking three times to establish a vice-like grip on the match.

The Greek star, a two-time Grand Slam finalist, broke again in the fourth game of the fourth set, giving his opponent few chances during a dominant performance.

His serene progress was briefly checked but he served out for the match at the second time of asking, completing the job in a shade under three hours.