Stefanos Tsitsipas of Greece plays a backhand return to Sebastian Baez of Argentina during their second round match at the Australian Open tennis championships in Melbourne, Australia, Jan 20, 2022. (ANDY BROWNBILL / AP)

MELBOURNE - World number four Stefanos Tsitsipas was made to work hard by Sebastian Baez on Thursday before raising his game to beat the upcoming Argentinian 7-6(1) 6-7(5) 6-3 6-4 and reach the third round of the Australian Open.

In the first clash between two former world number one juniors, Tsitsipas - a two-time Australian Open semi-finalist - dominated proceedings early on but the 21-year-old Baez, ranked 88th and making his Grand Slam debut, then showed why he is rated so highly.

The Argentine's big forehand Sebastian Baez troubled Stefanos Tsitsipas, but he found solutions and broke Baez's serve three times in the third and fourth sets to seal the contest with an unreturned serve on his second matchpoint

"It wasn't easy. I'm glad I overcame that obstacle today," Tsitsipas said on court. "Lot's of fighting, a little bit of swearing but glad to be in the third round.

"It was a pretty hot day today playing here but I tried to play with heart and it paid off in the end."

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Baez, who won six Challenger-level titles in 2021, came back from 0-40 down to hold his first two service games and then fought toe-to-toe with the French Open finalist to level the match at 1-1 after two tiebreakers.

The Argentine's big forehand troubled Tsitsipas, but the 23-year-old Greek found solutions and broke Baez's serve three times in the third and fourth sets to seal the contest with an unreturned serve on his second matchpoint on at the Margaret Court Arena.

"He is a great player. I haven't see him play much," Tsitsipas said, adding that he put a "bit more" into his strokes in the third and fourth sets.

"I wish him the best... one of the biggest forehands I have faced so I hope with the right work and right mentality he can reach his goals and make an impact in the game."

Tsitsipas will next meet the winner of the match between 26th-seeded Bulgarian Grigor Dimitrov and Benoit Paire of France.