You will always get some bad ratings as not every player will perform well all the time, there are a few factors that could contribute to this?.
1 Every player has a prefered position and formation/s which suit his quality!.
2 Having quality players around him.
3 Make sure you buy HOT PROSPECTS as these tend to be reall good!
4 Orders, try him with arrow and try phocus passing towards those players to get the best out of them!
5 keeping condition and morale to 90% or more
6 Buying wing players with the same side kicking foot!
There are many more I just cant remeber all of them!, if after all these factors he continue s to be poor then its time to get rid! , you have more than likely picked up a dud!, you have to sometimes think that seeing a 5* player with 4 or 9 is not always going to be great! so if he is not a HOT PROSPECT you are probably getting a poor player.