Australian Open: Rafael Nadal begins bid for 21st Grand Slam with win over Marcos Giron

Rafael Nadal began his bid for a men's record 21st Grand Slam title with victory over Marcos Giron in the Australian Open first round.

Sixth seed Nadal, the only former Melbourne champion left in the men's draw, beat American Giron 6-1 6-4 6-2.

The Spaniard is making his return to Grand Slam tennis after a five-month layoff with a foot injury.

"I have had very challenging months, tough moments and a lot of doubts," he said on court.

Nadal is the only member of the 'Big Three' competing in Melbourne after nine-time Melbourne champion Novak Djokovic's visa was cancelled on Sunday.

His sole Australian Open title came in 2009 but he won the Melbourne Summer Set in the build-up to the tournament.

He was rarely troubled against Giron, hitting 34 winners to help set up a second-round meeting with either home favourite Thanasi Kokkinakis or Germany's Yannick Hanfmann.

"You never know when you come back from injuries - things are difficult and you go day by day," Nadal, 35, said.

"But I'm staying positive. I won three matches and a title here last week."

• Berrettini through even though 'my body wasn't there'

Elsewhere, Wimbledon finalist Matteo Berrettini overcame stomach problems to beat American 20-year-old Brandon Nakashima.

The Italian took a medical timeout during the second set and wrote 'Imodium, grazie' on the camera lens after his 4-6 6-2 7-6 (7-5) 6-3 victory.

"I've been feeling sick with my stomach, let's say that," Berrettini said.

"I really held with my mental strength mostly, because my body wasn't there."

France's Gael Monfils continued his good form with a 6-1 6-1 6-3 win over Argentine Federico Coria, while rising star Carlos Alcaraz of Spain came through 6-2 6-2 6-3 against Chile's Alejandro Tabilo.

Canadian 14th seed Denis Shapovalov beat Serbia's Laslo Djere 7-6 (7-3) 6-4 3-6 7-6 (7-3) and Polish 10th seed Hubert Hurkacz advanced with a 6-2 7-6 (7-3) 6-7 (5-7) 6-3 victory over Egor Gerasimov of Belarus.