I'm willing to bet views have changed after Sevilla, TBH though Mata should be the one exiting, if we're bringing in someone more experienced.
Well unless he gets rid of someone, then having Lukaku, Martial, Rashford, Lingard, Mata, Sanchez and potentially a new attacker fighting for 4 spots is ridiculous, especially if you consider that normally only two attacking subs get onto the subs bench.
If Mourinho's intentions were to play Sanchez on the right, then we'd have balanced attacking options.
Lukaku/Rashford - Striker
Martial/Rashford - Left Mid
Lingard/Sanchez - Attacking Mid
Sanchez/Mata - Right Mid
As it is, Jose obviously prefers Sanchez down the left, which means one of Rashford or Martial will suffer, as they are also better on the left than right.
It also means we still need a right midfielder, as we've still only got Mata who can play there.