Some players especially goalkeepers need your faith. If you do not believe in them, they do not improve.
And you can show this faith by putting them in your top 11 - let them start the game. Or even play the whole game.
Initially, they might be rated 6, but the more you play them they grow in confidence and understand your orders.

My scout GK did this to me this season, I played a number of games with him which we lost (about 3 or 4 of them).
In about the fifth game, I started getting a commentary from him which I did not use to like: "Saphiu is coming out and clutches the ball to his chest".

I will like to state that having a 6 rating is not bad when the player is receiving good comments. But if he keeps losing the ball do not border about the rating. Just bench him.