When you play CT, the enthusiasm decreases in about 50%, and your defense and rebounding will be affected. If you go on playing CT, you will not see the effect because the CT effect is independent of the enthusiasm level. Below E=5 and playing CT your team always perform similarly, but when you go back to play Normal then your ratings will drop strongly during a few matches until you get back to E = 5.
This is my opinion, but some people don´t share it.
Good luck.
¡Me aburro! (Homer Simpson)