Valencia was signed by Ferguson in 2009 and won two Premier League titles under the Scot.
And the Ecuadorian, who departed Old Trafford this past summer, has explained what made Ferguson's team special.
Speaking to The Athletic, he said: "This was a team of absolute winners. I remember arriving at United and winning a game at the weekend. I thought: 'Phew, now we can relax a little.' Then straight away everyone was talking about winning the next game.
"There was never time to enjoy the wins. But that's what title winners do. I'd get to training: Patrice Evra, Wayne Rooney, Ryan Giggs were all in the gym, way before training started. I am thinking: 'These guys have Champions League winners' medals, they are multi-millionaires, and here they are in the gym at 7am?'
"Imagine that determination, that inner steel, that hunger. As a young player, what a lesson: these people are not only winners but they are addicted to winning.
"[They were] demanding, too. The players policed the dressing room. There was nothing worse than lateness from a young player, because 34-year-olds had arrived two hours before to do extra work.
"Do people realise these hard yards? They see results, who wins and who plays well, but they don't get to see the sacrifices.
"Giggs, for goodness sake! I got there when he was [in his] mid-30s and he's taking up yoga so he can keep winning and then he's leading the way in fitness drills. Amazing."