It was the ideal start for Djokovic, with the top-seeded Serbian steeling himself for bigger challenges ahead.

One of those could perhaps come against Juan Martin del Potro.

The Argentinian is again trying to put a good run of form together as he bids to add to the US Open he won in 2009, and he looked fit and healthy – a rarity for him since that 2009 success – as he got past Albert Ramos.

There was success too for 35-year-old Tommy Haas who beat Dmitry Tursunov 6-3 7-5 7-5, while Australian Bernard Tomic survived heat exhaustion to see off Sam Querrey.

Tomic took the first two sets on tie-breaks but wilted in the third and fourth as a lack of breakfast plus a sun-drenched Court Three took its toll on him.

He broke the big-serving American in the eighth game of the decider, though, and went through to the next round.

American James Blake, considered a challenger by some in the past, saw off Thiemo De Bakker for the loss of just six games, while Germany’s Jan-Lennard Struff had a similarly easy time of it against Blaz Kavcic.

Philipp Kohlschreiber had to deny he had quit his clash with Ivan Dodig on Court 18 in disgust after walking off when 2-1 down in the fifth.

Last year’s quarter-finalist took the first two sets but lost the next pair, before shaking hands after three games of the fifth.

The German had reacted angrily to a number of calls during the match but said his struggles with flu had left him “angry and sad” rather than anything more sinister.

Australian James Duckworth worked hard to recover from two sets down against Denis Kudla before collapsing to a 6-4 6-2 3-6 4-6 6-1 loss, while there were also victories for Leonardo Mayer, Jesse Levine, Kevin Anderson, Michael Llodra and the impressive 12th seed Kei Nishikori.