Martial plays either as a striker or as a LW. Now According to transfer rumours we're aiming to get Graelish, Sancho and a striker (Dembele?). Meanwhile we'll get rid of Lingard and Periera while Sanchez will return to the fold.
Graelish is more comfortable as a LW, Sancho as a RW (although he can play on the LW) and Dembele plays as a striker. That means we'll have
LW: Rashford (FIRST TEAMER), Graelish, Sanchez, James and Martial + Sancho can play there.
STK: Dembele (FIRST TEAMER), Greenwood, Sanchez and Martial
RW: Sancho (FIRST TEAMER), James, Chong, Sanchez.
Graelish and Rashford are better then Martial on the LW while Dembele is better then Martial upfront. Will Martial accept a reserve role? I doubt it.