Hi guys!

I've been always struggling with player form.
Lately I have a few star players who have suddenly under performed.
They started the season with form 7/8 but now are scoring only 5/4.

My goalkeeper is an example. I end up losing games cause he lets in too many goals.

Anyone have suggestions on how to deal with this?
Anyway to improve players form when it starts to decline or should I just sell and get a replacement straight?