Van der Sar then saved all three Chelsea penalties - from Claudio Pizarro, Frank Lampard and Shaun Wright-Phillips - as United lifted the silverware.
"Edwin's experience came through there. He studied particularly Lampard's penalty-taking and that experience has got the result for us today," said Ferguson.
"There was nothing much between the two teams in possession terms but we did create our chances and I think for that reason we deserved to win.
"They obviously missed (Didier) Drogba. He is a very important player for them."
United had expected Drogba to play and that prompted the decision to start with both Mikael Silvestre and Evra.
"We thought Drogba would be playing so we wanted to make sure we had a stronger back four in terms of physical appearance, and with Nani not 100% fit we preferred to get balance (in midfield) with Ronaldo on the right and Evra on the left," said Ferguson.
"And Evra did quite well for us actually. He is a very quick lad, he has made a good goal."