You might be underestimating the impact on morale. Premiership games can be wars. You need a united dressing room. If the dressing room knows a player is on his way, and especially if that player is as influential as Sanchez I think the message it sends is terrible. Technically you might think better to have him than not, but I don't think it's as simple as that.
We won't be a better team without him. Or get better results. That's what it should boil down to.