Quick look at United over the summer:
Out/retiring: Ferdinand, Vidic, Evra, Giggs
Possible out: Nani, Buttner, Hernandez
Starting XI (example formation):
De Gea
Rafael? - Jones? - xx - xx
Mata - Fellaini? - xx - Januzaj
Rooney - van Persie
Possible bench/rotation:
Lindegaard
Amos
Smalling
Evans
Keane
Varela
Cleverly
Fletcher
Carrick
Kagawa
Young
Valencia
Lingard
Welbeck
By my reckoning they are going to need at least 3 and possibly 6 starting eleven players in the summer, two left backs total, plus perhaps another striker (depending on Hernandez or returning Henriquez).
If they are ever going to make a player out of Jones they have to give him a run in his best DC position, and Fellaini for the outlay will need another season.