"I've spoken to Michael and he is obviously delighted as he was getting frustrated by the lack of opportunity he was getting at Sunderland and has a lot of friends at Cardiff.
"He is over the moon, I'm delighted and Dave is grateful that we've got in the players he wanted during the transfer window."
Chopra's move is Cardiff's third signing of the January transfer window following Quincy Owusu-Abeyie and Chris Burke's arrival at Ninian Park
The former England under-21 international signs on at Cardiff for the third time and enjoyed an impressive loan spell earlier this season.
Chopra, a former Newcastle United trainee, was a fans' favourite at Cardiff during a successful 22-goal season in 2006/07.
He caught the eye of the then Sunderland boss Roy Keane and the Stadium of Light signed him in a £5m deal in the summer of 2007.
But Chopra returned to Ninian Park in November for a successful five-goal two-month loan spell and Ridsdale then spoke of his desire to re-sign him permanently.
New Black Cats boss Ricky Sbragia recalled Chopra when he replaced Keane to reassess his options.
Sbragia did say on Sunday that his club would consider a strong bid from Cardiff but he wanted Chopra to stay at Sunderland.
"If it's right for the club I'd like to keep him," he told BBC Radio Newcastle on Sunday.
"But if they come with a bid we think is good enough and it's money we're looking for then we'll consider that."
Subsequently a Sunderland statement confirmed on the club website on Monday: "Michael Chopra has rejoined Cardiff City on loan until the end of the season.
"Sunderland have agreed to let the striker sign for the Bluebirds until May when he will complete a permanent move to South Wales in a deal worth nearly £4m."
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