Wayne Rooney's second-half leveller ensured Sir Alex's men got the point they needed to secure a record 19th championship and spark memorable celebrations at the final whistle.
"It was here last year that we more or less lost the league so it's nice to come back and make up for it," Rio told MUTV. "We did it the hard way today. We gave away a soft goal, but managed to stay on our feet and get back up. We put a hard graft in and kept on persevering and got our rewards.
"You can't put into words [what this feeling means] and it was great to celebrate with the fans at the end. They follow us all over the world and give us great support and they deserve this."
Ferdinand paid tribute to team-mate Ryan Giggs afterwards, insisting he is an inspiration to all the players at the club. "He's looking down on us from above!" said Rio in reference to Giggs' 12th title triumph. "What can you say about him? It's difficult to put into words what he's achieved as a player in terms of medals. But it's been the way he's done it which has been so impressive. We're all trying to get to where he is."