Stansfield seems like a good player, but was in a hot streak of finishing last season ( i.e. he scored significantly over his xG , and it's usually expected that can't be sustained over a longer period)
also looking at his stats he does very well with things like pressing from the front and carrying the ball forward, but there isn't much evidence that he can be an effective aerial presence.
of course you'd have to look into that deeper to see if it's just something that isn't in his game, or more a reflection of how the team were looking to use him.