Rafael Nadal answered doubts about his fitness in emphatic fashion as he began his Australian Open campaign with a thumping win over Victor Estrella Burgos.The world number one came into the tournament without having played a warm-up event following knee problems at the end of last season.But, he was anything but rusty as he raced to a 6-1, 6-1, 6-1 win in just an hour and 34 minutes.Veteran Estrella Burgos was not expected to provide too much of a challenge to Nadal and so it proved.The 37-year-old from the Dominican Republic earned a rousing reception when, after a long game, he broke the Nadal serve to avoid losing the second set to love.But, it was simply a minor detour for Nadal who, in his first match since his uncle Toni stopped travelling as his coach, could barely have asked for a better outing.Elsewhere, things were equally straightforward for Australian title hope Nick Kyrgios, who promised a new mature approach ahead of the tournament and largely delivered in a 6-1, 6-2, 6-4 victory over Rogerio Dutra Silva.Kyrgios received a code violation for swearing at a spectator, who he felt was being too noisy, but there were no alarms on court.The 17th seed is unbeaten so far this season having won the warm-up event in Brisbane and faces Serbian Viktor Troicki in round two.

Elsewhere, a terrible day for America in the women’s draw was compounded by defeats for eighth seed Jack Sock and John Isner.

Sock, who broke into the top 10 thanks to a brilliant end to last season, was beaten 6-1, 7-6 (7/4), 5-7, 6-3 by Yuichi Sugita of Japan, while 16th seed Isner lost 6-4, 3-6, 6-3, 6-3 to Australian Matt Ebden.

Third seed Grigor Dimitrov, a semi-finalist 12 months ago, eased past qualifier Dennis Novak 6-3, 6-2, 6-1 to begin his campaign in fine style.

It was a trickier first outing for sixth seed Marin Cilic, who dropped a set to Vasek Pospisil before coming through 6-2, 6-2, 4-6, 7-6 (7/5).

Denis Shapovalov won the battle of the teenagers 6-1, 6-3, 7-6 (7/5) against Greek Stefanos Tsitsipas, but US Open finalist Kevin Anderson lost in five sets to Britain’s Kyle Edmund.