I have no idea who, we need a striker who can add a few goals really. Martial scored 4 goals in 1480 minutes, this is a terrible outcome and honestly we don't even know what happened to him.
Having a random, fit striker for entire season is better than last season Anthony. But - it all depends if we see a future with Martial, if we do than fair enough, but if there are serious doubts than I would sell him. Like mentioned before, it will take weeks, possibly months for him to get up to speed, Cavani isn't ready either, Rashford is out, so it'd be crucial to get ANYBODY for the beggining of the season.
The difference in Martial 19/20 and 20/21 is something I have never seen before in a footballer (without any particular reason that is). This is a big worry.