Jose Mourinho's men remain five points clear of Manchester City at the top of the Premier League after holding the champions to a 1-1 draw at Stamford Bridge on Saturday.
The London club also face a League Cup final against Tottenham in March and take on Paris Saint-Germain in the last 16 of the UEFA Champions League.
Mourinho was unable to call on key duo Cesc Fabregas and Diego Costa due to injury and suspension respectively against City, while Gary Cahill dropped to the bench.
And defender Ivanovic feels the spirit in the side and the strength in depth Mourinho can call upon is vital.
He told the club's official website: "The most important thing in football is that every player who gets their chance has to give everything for the squad,
"This helps make each other better and it helps us on the field. You can see the reaction of every player, even when they're not playing. They give everything. It's a good example and it's the only way to win."
The Serbia international, who made his 300th appearance for Chelsea at the weekend, feels it is still all to play for in the Premier League title race despite the strong position Chelsea find themselves in.
He said: "You need to go over the limit and to find motivation inside you. Sometimes the extra pressure is what we need to feel. We still have a long way to go - 15 games is a long way - and we have to stay focused.
"It's very difficult to judge at the moment but we are the leaders and we know our way and how we play. Our style is to fight and to give everything every game."
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