Try to bench him for 3-4 days.
I did the same for a player with 5-6 form, now he is always playing for 7-8. As well if your player has 2 positions being able to play try using him in his other position.
I had recently this experience with a player being able to play as DMC and DML and after comparing him with a couple of other DMCs of my squad I saw that he was much lighter and faster so I tried to use him as a DML and he passed from a 7 form to 7-8 and scored a couple of goals already after 2 matches. This player had several injuries since the begining of the season and now he is in perfect shape.
Good luck bud