"It was a bit of a no-brainer really," explained Ferdinand.
"Jonny was at a stage where he wanted to play every week. He had been at Sunderland the season before and he didn't want to come back and play reserve team football again with United.
"He wanted to play first team, which is the same argument for any young player.
"The question he had to ask himself was whether he wanted to go and play for a team mid-table or be part of a squad where you will have chances to play in a title-winning team or one that wins the European Cup.
"The manager didn't want to let him go anyway but I know where I'd like to be playing my football and Jonny came round to thinking that it was better to be a part of the squad and play when the opportunities came so common-sense was the winner in the end."
As it turned out Evans made 32 appearances last term, far in excess of what he could have previously imagined.
In addition, Evans collected his first Premier League title medal, with appearances in the Carling Cup final and FIFA Club World Cup.
"He is a fantastic young player," said Ferdinand.
"It's always difficult to see the best of centre-halves at an early age. There's always the chance of them making mistakes.
"But Jonny keeps that to a bare minimum. He has got a cool head on his shoulders.
"He sat back and watched for a few years when he was younger. Then he went to Sunderland and did very well, so, for obvious reasons, they wanted to buy him.
"But he stuck to his guns, stayed here and last season he had opportunities to play. And when he did so, he was fantastic."