The 22-year-old ha lost his way at Old Trafford over the last year and is now ready to look elsewhere for first-team football.
The high-flying Bluebirds are now ready to make a move for him, in a bid to bolster their promotion push.
Cardiff have also been linked with three Welsh internationals in the shape of Andy Melville, Steve Jenkins and John Robinson.
City manager Lennie Lawrence confirmed his interest in the four players.
"We have an interest in most of the players mentioned - that's not to say that they will all be pitching up today or tomorrow," he told the Welsh media.
"It would be reasonable to assume that one player - who may or may not be on that list - will be with us sooner rather than later.
"The current players are doing well, but this is a big club with limitless ambition.
"We're trying to strengthen the squad to prepare for all eventualities. We have to satisfy the fans."
Melville, 34, is currently considering his future at Fulham, as is Huddersfield Town captain Steve Jenkins.
The 31-year-old Robinson is again struggling to earn a place in Charlton's starting XI and could be tempted by a switch to Ninian Park.
