Fellaini was moved to a deeper midfield position by his manager during the second half as the Blues trailed Sunderland 1-0 .
After the switch, the influential Belgian star promptly scored the equaliser before setting up the winner for Nikica Jelavic just two minutes later.
Fellaini told evertontv: "The manager changed the tactics and when he did I scored and got the assist, so it was good for the team.
"We started well but after 25 minutes we weren't playing as well and weren't creating enough chances. Sunderland started to play well.
"But the team kept going and in the end we got the win."