Terry has returned for the last two games, which has seen Chelsea ship four goals.
"We need every player but especially John," said Ivanovic. "He is a real warrior and leader of the team, especially as he's captain. He is a very important player for us and his injury came at a bad time. It has been a very difficult season for him but he's back now and he will help the team in the future. It's always better to have him on the pitch, this kind of player who can shout and organise. He can motivate you and every second he supports you.
"He does well not just for himself but his team-mates. It is important to have someone like him on the field, we have missed this."