Saw on Twitter:
Zlatan in 2016/17 - goal contribution every 110 mins (35 in all comps)
Lukaku in 2017/18 - goal contribution every 115 mins (35 in all comps)
................... Martial's first season at #9 - goal contribution every 101 mins (33 in all comps, with significantly less minutes than the other pair).
So there's literally 0 drop off in output from the top "traditional" number 9s we've always been hellbent on (in fact, a little better. And he's won more penalties too which should be a more highlighted stat, imo) and he's providing a helll of a lot more for the team with his overall game (ability to provide rotations, his technique/associative game in comparison to Lukaku, his pressure on the ball & pace in comparison to Zlatan, etc.). I don't think I'd consider swapping him for any other striker on the planet bar maybe Benzema or Firmino based on how we want to play.