Ronaldinho has the same ratings in league and CL.
I 'm not saying that a player can have good performance only in one competition. It can be League + CH.L. or Cup

the CL and Cup starts very often with some very weak opponents, this alone would make the stats uneven
even if it's an easy game and you have a domination, still you can see one player scoring half of the goals of the team while others scoring only one goal.

This season, day 10 :
Willian still don't like CH.L.
Mythbusters of top eleven-d10-willian.jpg

Ronaldinho prefers it
Mythbusters of top eleven-d10-ronaldinho.jpg

and Ronaldo, the new comer, also looks like a CH.L. guy
Mythbusters of top eleven-d10-ronaldo.jpg