Here a example of Key player, called Arsenal:

Click image for larger version.  Name: t4 key player 1.jpg  Views: 35  Size: 64.3 KB  ID: 35096

Click image for larger version.  Name: t4 key player 2.jpg  Views: 33  Size: 66.4 KB  ID: 35097

This season for example I bought 2 MC's because I felt like something don't work with what I had. 1st one called pala kontol, that was invisible 4 matches, never seen his name in a match, but in his last team he had very good statistics.
Then I bought Struthers, that have 8-7-7 as ratings but, in 3 matches scored 1 and assisted 1, and now with this player kontol scored 3 of the 4 goals in 3 days...

Think in that too, 1 player can play better or worst with another nearly.
Don't look at the stars, prove, prove, prove.