Mata completed his club record £37.1 million move from Chelsea on Saturday.
But he has not played since New Year’s Day, when he started Chelsea’s 3-0 win at Southampton, after falling out of favour at Stamford Bridge.
However, manager Moyes believes Mata will be able to face Ole Gunnar Solskjaer’s team and plans to give him his United bow at the first possible opportunity.
Moyes told MUTV: “Juan’s not too far away from [full] fitness. I know he has missed a few games and maybe not started quite as many games as he’d have liked, but I’d like to get him involved against Cardiff.”
Mata scored on his last appearance at Old Trafford in May when he earned Chelsea a 1-0 victory and became the last player to get a winner against Sir Alex Ferguson’s United.
He last appeared on the bench when he was an unused substitute for Chelsea as they beat United 3-1 last Sunday.
Written by Steve Milne
