Former Liverpool and Tottenham Hotspur player Jamie Redknapp has questioned Manchester United manager David Moyes's transfer activity.
The Scotsman has brought in two major signings since taking over from Sir Alex Ferguson at Old Trafford at the end of last season.
Fellaini arrived from Everton in the summer, while United secured a club-record fee of around £37m to lure Juan Mata away from Chelsea during the January transfer window.
While Redknapp has hailed Mata's ability, the retired footballer believes that Moyes is playing him out of position because Wayne Rooney, who recently signed a new bumper contract, stands in his way.
Redknapp wrote in the Daily Mail: "Moyes has only made two big signings, but they are not working for him. He spent £27.5m on Marouane Fellaini, but he has never looked a United player. And I'm a big fan of Juan Mata, but you don't spend £37m on a player and play him out of position.
"United have always had fantastic wingers but Mata is not a winger, and you make yourself look worse by playing him there. He needs to play in that number 10 position, but how do you sacrifice a man you're paying £300,000 a week?"
After losing 3-0 to Liverpool on Sunday, United sit seventh in the Premier League table, 12 points adrift of a Champions League place.