What if I tell you that in 17/18 Martial had more tackles per game than Rashford, more carries per game, that was more likely to tackle in our own third than Rashford. Now Rashford had more pressures per game than Martial. Now what if I tell you that people have the impression that Rashford did more than Rashford because Rashford concentrated his defensive contribution in the opposition third, visually it gives you the impression that one is doing more but it ignores that the other was better at tracking back and being involved defensively at all the other levels. And when it comes to effort nowadays we underestimate the action of carrying the ball a lot, Martial was doing it at a far higher volume than Rashford.
With that I can answer a previous question that you asked. When you look at someone like Dembélé take into account the fact that he will track back, he may not be in time but generally he makes the effort, he also carries the ball and lead counters at high pace for the entirety of his time on the pitch, if we are realistic you can't expect a player to attack at the highest intensity and also defend at the highest intensity, it's not a thing. The players that are supposed to carry a heavy load on offense or defense are expected to have smaller roles in the other phase.