Does player form ever improve?

[Steppenwolf]

Got an 18 year old high 5 star keeper who is expensive but has thus far put in 4 or 5 out of 10 performances. Will this ever improve?

This is performance of my former striker in 6 seasons. As you can see, he played poorly in his first season, but in next 2 seasons he got rating 6 only once. Then he had poor 4th season, but he again played for 7 and 8 in 5th season.