Jumping the gun a bit there, he didn't 'not rate' Mata, he simply preferred Oscar in the number 10 role as he believed Mata didn't offer the same in his system. I think it's safe to say he's since learned that players like Oscar, Hazard, FABREGAS... these guys have no spine, whilst at the same time, he's watched Mata rescue the day for United on many occasion, I'm not overly convinced that Mata is on his way out of Old Trafford if and when Mourinho turns up, I think Jose will have some making up to do with Mata, who has as it happens, wiped the floor with Oscar since he turned up here.
Giggs, that's another story, whether he was ever being 'groomed' as our next manager is unknown, but he's not shown very much, sitting in silence, murmering in the ear of Van Gaal, sitting with puzzled looks on his face next to Moyes and Steve arsehole Round, unquestionably brilliant player but that never means good management material. Maybe it's his time to leave.