"It was something we talked about with Jorge Mendes [Ronaldo's agent]," Mirabelli told Italian television show Sportitalia.
"We knew there could be problems with Real and Ronaldo. We did everything, but then the Chinese owners blocked the deal because it was not sustainable.
"With the current owners, CR7 would have been a Milan player."
Ronaldo has since gone on to score 53 goals in 75 appearances across all competitions for Juve, winning the 2018/19 Serie A MVP and 2019 Serie A Footballer of the Year awards in the process.