United will come up against Van Persie in Sunday's trip to the Emirates, live on Sky Sports HD1, hoping to keep the Premier League's top scorer at bay.
Ferguson is a big admirer of Van Persie and admits the club watched him while at Feyenoord before opting against making a move for the player.
"I remember going to see Van Persie play for Feyenoord reserves, way, way back," said Ferguson.
"We were definitely interested, but the day we went to see him he didn't play the full game.
"He was either sent off or he walked off, I can't remember which. We ended up leaving it, we didn't make a move for him.
"I don't think we saw enough of him to make a decision, whereas Arsenal were much closer to the situation at the time and they eventually got themselves a terrific player."
Ferguson admits Van Persie has developed into one of the best players in the world and he believes he is now Arsenal's key performer.
"He's turned out to be a fantastic player," added Ferguson. "Top teams usually have a player who can make a difference and Van Persie can. You look at Messi at Barcelona, Ronaldo at Real Madrid, Silva at City and for many years, Drogba at Chelsea. It's a fact.
"Van Persie's form and his goalscoring have been fantastic. We have to hope he's not at his best against us.
"He's scored 18 goals in the league and his form is fantastic this season."
