Despite their huge lead at the top of the table, Vidic reveals he still has the memory of last season's eight-point lead evaporating in the space of just four games fresh in his mind.
Despite watching much of the season from the stands, after rupturing cruciate ligaments in December, the Serbia international says the memory keeps his United side focused.
"You are never sure until you have the trophy in your hands," said the Serbian.
"I do think about last season. It is still fresh.
"If we hadn't experienced that people would be saying it is already done.
"But that kind of thing keeps you sharp.
"It is good for the team and the players because we don't want that to happen again.
"It was bad last year but this year it is working for us."
Vidic agrees with manager Sir Alex Ferguson in finding it difficult to believe United could have established such a lead with nine games remaining.
"We didn't expect this situation," he said. "No-one expected did.
"We are happy with it but we still have big games to play.
"We have to play City, Arsenal, Chelsea, West Brom, Swansea. They are teams who can hurt you. They are tough games.
"Teams at the top and some who are fighting relegation. We just have to keep winning."