I agree. Although they play in different positions and are different players, Grealish just has far more good influence on his team's game than Martial, who drifts in and out. What's more, he makes that impact while being extremely tightly marked. Forget Arsenal as they were just appalling after raising their game against us, but look at his performance against Southampton two weeks ago. Two men, Romeu and KWP, were tracking him all game, but he still scored a goal, assisted two and drew a load of fouls as usual, a very useful asset when you need a goal or to relieve pressure. So, in an ideal situation where we bought Grealish next season, I'd use:
DDG
AWB CB Maguire Telles
DM
Bruno VdB
Rashford Greenwood Grealish
Why? Grealish, Rashford and Greenwood are all players with a higher ceiling than Martial imo. Also, we'd be able to play Grealish in his favoured position as an inside left. Therefore, if he came, Martial would have to be the fall guy. People won't like it but it would be best for United.