Big guns Alexander Zverev, Dominic Thiem and Juan Martin del Potro win

Alexander Zverev, Dominic Thiem and Juan Martin del Potro are all safely through to the second round of the Mexican Open.

Second seed Zverev had no problems seeing off Mackenzie McDonald 6-3, 7-5 in one hour and 21 minutes.

Next up for the German is his compatriot Peter Gojowczyk, who beat Mexican wildcard Lucas Gomez 6-3, 6-2.

Former US Open winner Del Potro was also in good nick as he brushed aside Zverev’s older brother, Mischa, 6-1, 6-2 in just over an hour.

However, 2016 Acapulco winner Thiem didn’t have things all his own way against Cameron Norrie as he had to bounce back from a second-set setback to beat the British qualifier 6-3, 5-7, 7-5.

He had a match point at 5-4, but Norrie broke and then claimed another break to take it to the decider.

“Yeah, very tough match. Should have been over earlier in the second set but didn’t close it out very well,” Thiem told “It went over three sets and ended up a pretty big drama at the end, I would say.

“I was 5-4, 30-15 and then I made some easy forehand mistakes to lose a little bit of my confidence. It shouldn’t’ happen but yeah, what can I do now? The main thing is that I won and that’s all I care about.”

Canadian teenager Denis Shapovalov claimed the big scalp of Kei Nishikori as he beat the former world number four 6-7 (3-7), 6-3, 6-1.

“I just kept fighting. I got my break, and the momentum went from there,” Shapovalov said. “It’s tough to play him. He’s so solid. He moves extremely well. It was an extremely difficult match for me.”

Australian Open semi-finalist Hyeon Chung is also through after he beat American Donald Young 7-6 (7-5), 6-1 while Rio Open winner Diego Schwatzman beat Fernando Verdasco, the man he defeated in Sunday’s final, 6-2, 6-4.