Chelsea face the League One club in an FA Cup fourth-round replay and after the Stamford Bridge outfit recorded a 1-0 win over Sparta Prague in the Europa League on Thursday, Ivanovic believes that it is important his side maintain their winning run at the weekend.
Ivanovic told reporters: "It was a very important game for us to win and to keep the momentum going.
"The lack of consistency has been very difficult for us, but we are a team that can build and we have to think about this.
"We have to improve every game, every session and we hope it will be fine in the end."
The winners of Sunday's match will play Middlesbrough in the fifth round.