Nishikori through in Mexico

The world number five didn't have it all quite his own way though, requiring an hour and 37 minutes to see off his Colombian opponent 6-3, 7-5.

Nishikori's serve was not at its best on the day, with the Japan star failing to notch up a single ace while only landing 57 percent of his first serves.

However, while he came under pressure on his own serve, Nishikori was able to save six of the seven break point opportunities that Gonzalez created. Conversely, Gonzalez could only save seven of 11 break opportunities and that proved the difference.

Earlier, defending champion Grigor Dimitrov's title defence began with a 6-3, 5-7, 6-0 win over Filip Krajinovic.

The match was an incredible one in that Dimitrov created an incredible 27 break point opportunities, although he was only able to capitalise on eight of them.

The third seed will face American Ryan Harrison in the second round after the qualifier was 4-6, 6-2, 4-2 up when compatriot Donald Young retired.

Elsewhere there were wins for Yen-Hsun Lu, Viktor Troicki, Bernard Tomic and Andreas Haider-Maurer.