Rabiot (free), Ndombele (52 m), Tielemans (40m), Rodri (70m) and likely how the window is going there will be more added to that list. Every single of those individuals will walk into the starting eleven.
Longstaff has under 20 appearances as a professional at the top level, we needed midfielders when Herrera was here now he's gone we need to replace him. Longstaff is not an adequate replacement for any of the calibre of central players we need. Fernandes is not a central midfielder, In a system where Solskjaer has played three central midfielders and a double pivot system tactically it doesn't make sense and no credible source has reported our interest in Fernandes.
If Saul (with a 134 million release clause) is a credible option then the club must have changed owners in the last 24 hours because you can be certain we will not pay that money for anyone. Again no credible sources that have declared our interest.