A hamstring injury sustained on international duty left him sidelined for a month and then an impressive comeback display against Bolton was ended prematurely by a red card.
The towering midfielder admits his sending off - picked up for retaliation - was foolish on his part, and that he has spent his time exiled from the first team analysing his behaviour.
Fellaini says he has learnt a valuable lesson and is now fully fit and desperate to prove his worth to the team - starting at Stamford Bridge.
"I have had a frustrating time," the 23-year-old told evertontv. "I was injured then I got back training again, the manager gave me confidence, I played again and then was sent off.
"It is positive in a way because I have thought a lot about it and I know it is my mistake, my error and I will not do it again.
"I have trained hard while I have been suspended and am ready to play. The manager will decide whether I play or not but I am ready."