He's been very poor, consistently takes that extra touch that gets his shot blocked. He was on a little run and now it's gone. Too much hot and cold to be the front man long-term, this was the season where he needed to validate last season's performance to answer his CF critics. He's not lived up to it.
That being said, I think Martial is still a very important player to United's best moments as presently constructed. I wouldn't be as shocked as some that he gets it together in the coming months and has a big impact, but he's not going to be the CF of the future for this club. He can make his place on the left wing and compete with Rashford. RW is most important, CF is next.