Marrero said he was surprised that he was under investigation.
"I was at home packing my suitcase because tomorrow, Friday, I'm heading to Germany, and this news caught me by surprise. I had no idea. What do want me to say? Just like always, go ahead and investigate because I'm very much at ease," Marrero told EFE.
This is the second time Marrero has been investigated for purported match-fixing after a similar incident at a 2016 Australian Open mixed doubles match.
Marrero and his then partner Lara Arruabarrena, along with opponents Lukasz Kubot and Andrea Hlavackova were all investigated but subsequently cleared by the Tennis Integrity Unit.
Marrero is ranked No.54 in doubles and has ranked as high as No.5 in doubles in his career.
His partner Verdasco is an accomplished singles player who reached the 2009 Australian Open semifinals, losing to countryman Rafael Nadal, and has a career-high singles ranking of No.7.