Being short on confidence might explain Rashford not being able to complete a five yard pass, trying to dribble through 4 defenders, terrible shooting and always, always being offside.He's just short of confidence. He's one of those who's bottom level is horrible when he's in poor form.
But being in poor form doesn't excuse you from pressing, tracking back, running on to passes, running onto deflected shots and walking around looking like your dog died out on the pitch