The 36-year-old says he will convince the Mexico international, who has failed to live up to the promise shown as a teenager, to join the newly promoted Liga side this summer
The 24-year-old, who was relegated with Mallorca this year, is reportedly seeking a move away from the Islanders during the summer in a bid to boost his chances of being selected for Mexico's World Cup campaign.
Valencia, as well as MLS outfit LA Galaxy are also monitoring the former Barcelona starlet, but ex-international team-mate Franco says he will persuade Dos Santos to join newly promoted Villarreal.
He told Marca: "I have not spoken with him, but I have spent lots of time with him in the Mexico team and I can say he is a great player.
"Gio is fast, strong and has some great qualities and if I speak to him I will try convince him to join Villarreal."
Franco enjoyed a three-year spell with the Yellow Submarine from 2006 until 2009, netting 20 goals in just over 100 appearances.
Dos Santos has a contract with Mallorca until June 2016.