Rafael Nadal powered through to the last eight but second seed Alexander Zverev fell on Wednesday, while Grigor Dimitrov survived.
Heather Watson was too good for Kateryna Bondarenko in the Mexican Open second round.
Karen Khachanov will be the next man to try and stop Novak Djokovic, who now holds a 15-0 record in 2020 after winning again in Dubai.
There will not be a farewell tour for five-time grand slam champion Maria Sharapova, who announced her retirement from tennis on Wednesday.
ATP Tour stars Novak Djokovic and Stefanos Tsitsipas led praise of Maria Sharapova following her sudden retirement.
Russia's Maria Sharapova has called time on her tennis career after 19 years.
In action for the first time since the Australian Open, Rafael Nadal was untroubled in Acapulco.
Venus Williams wasted seven match points in a first-round loss at the Mexican Open.