The Colombia international forward joined the Red Devils on deadline day on a season-long loan deal from Monaco.
With the 28-year-old expected to make his debut this weekend against Queens Park Rangers, Saha expects Falcao to make a big impact at Old Trafford.
"Falcao signing for the club is something that is sweet both for him and Manchester United," the Frenchman told Sky Sports News.
"There is no doubt that he will definitely be a success at Manchester United. He is a top goalscorer, a busy striker who knows how to create space and is very difficult to mark.
"He has got that special instinct that great strikers have. It is something I've certainly never had. I had the ability to score from distance but I was not of his calibre."
Saha scored 48 goals in 121 games for United between 2004 and 2008.