After eight years at Stamford Bridge, the Ivory Coast star signed for Chinese side Shanghai Shenhua for a reported 200,000 pounds ($314,000) a week, making him the highest-paid player in China and in the top bracket globally.
Ferguson, speaking in Shanghai ahead of a friendly against Drogba's new team on Wednesday, said he may have pursued the 34-year-old if he had decided against going overseas.
Asked if he was ever interested in Drogba joining the Red Devils, Ferguson said: "I think that the decision was his anyway because he said he was going to leave Chelsea and not play in the English league -- that eliminated everyone. I could have been."
Drogba decided to join his old Chelsea team-mate Nicolas Anelka at Shanghai, saying he wanted a "new challenge" outside of England's top flight.
He made an instant impact on his debut in the Chinese Super League, setting up his team's equaliser in a 1-1 draw away to Guangzhou R&F on Sunday.
United and former England defender Rio Ferdinand said Shanghai will face a test of how much they have developed with their new signings when the teams meet.
"I'm looking forward to it. Obviously there's been a lot of excitement and press coverage about Didier and Anelka coming to Shanghai so it's a great game for both clubs," Ferdinand said.
"Shanghai gets to see where they are at, and obviously at this stage it's our pre-season and the main focus for us is to get to another stage of fitness and get through the game unscathed by injuries."