We've been lacking quality so he signed a world class player that can actually make runs and cross. Would a right winger have made more sense? Probably, but there's not that many available. And don't see the point in playing your best players out of their favoured position for the sake of a young very on/off player, personally. The funny thing is, Martial FC didn't want him on the left in the first place but now Sanchez is there that's the main problem.It's not an inept attack. Mourinho has chopped and changed his XI every game. Even after tht 3-2 win you still can't really identify his system, style or team. Which is why we are in a situation where players might want out. Rashford scores two vs Liverpool but is on the bench vs Man City. He decided to sign Sanchez to play in a position that was already being filled by Martial/Rashford.
Sanchez's arrival saw Martial shunted to the RW when he was actually in a bit of form.
Martial needs to stake a claim in whatever position he gets an opportunity in. Ronaldo did, and the way people go on about Martial, he should be able to at least not be shit on a different side.