United had the luxury of having stability with SAF.
Towards the end of 2007-2009 our spine essentially managed themselves. We saw a title challenge, European cup final, and a league cup final in that time.
The real question is whether that United side could project that same level of competitiveness without SAF. A huge portion of which were already heavily influenced by him. Rooney, Hargreaves, Nani, etc.
We’ll never know.