It has recently been reported that Chelsea were desperate to sign the 26-year-old in this summer's transfer window, and they have already had a £55.2m bid rejected by the Italian champions.
Marotta has indeed confirmed that a bid from the Premier League champions arrived, but Juventus were not interested in parting with a player that enjoyed an impressive 2016-17 campaign in Turin.
"Our desire is to not sell any of our most important players," Marotta told Corriere dello Sport. "We said no to a very good offer from Chelsea for Alex Sandro.
"But we know that we are competing with clubs that are in a position to offer wages that are not rational for us. And players are always their own boss. I do not know how Alex Sandro reacted."
Sandro, who joined Juventus from Porto in the summer of 2015, scored three times in 43 appearances for the Italian giants last season.