Ferguson elected to pair youngster Jonny Evans with Rio Ferdinand at the heart of United's defence for the Wembley final after the England player forcibly requested that he be handed a rare start in the competition.
Evans was rewarded with his starting place for being a mainstay of the side that played in the earlier rounds of the competition with Vidic only coming on as a late substitute as the game went in to extra-time.
Ferguson stuck with his policy of keeping a settled side for the least important of the domestic honours but only when it was too late realised that Vidic himself had in fact played in three previous rounds.
'With the League Cup it was simple - the ones who started the competition would play throughout,' said Ferguson.
'The only mistake I made on Sunday was Vidic. I didn't realise he'd played three games in the competition.
'But the reason I played Rio was because he's missed so many games since December with his back problem. I needed to get him back.
'Big defenders need to play games. Rio and Vidic will be a solid partnership now until the end of the season.'
Last night, Manchester United reestablished a seven-point lead at the top of the Premier League, with a further game in hand on both Liverpool and Chelsea, with a hard fought 2-1 victory over Newcastle at St James' Park.