Mourinho bore the brunt of the Blues' dreadful start and was sacked in December with his side stranded in 16th position in the Premier League.
Long-time club servant Ivanovic is adamant the players - not the Portuguese coach - were to blame for the poor run of results and acknowledged Abramovich's frustration at the situation.
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"Jose didn’t change. He didn’t change the way he prepared the game," the 32-year-old told the Daily Mail. "He didn’t change the way he treated us. He didn’t change anything. He was the same.
"Football is about players. The managers are not on the pitch. It is 11 against 11. You have to be better than your opponent and, at the beginning of the season, we weren’t.
"The players were more responsible for that situation than the manager. Of course it is difficult in football to change 25 players halfway through the season.
"But I think at this club if [Abramovich] could have, he would have changed all of us as well. It’s difficult to say it was only one guy’s responsibility."
Ivanovic claims the players were all mentally prepared for the beginning of the new campaign, with Mourinho emphasising to the players how difficult it would be to retain the title.
"We didn’t know what was going wrong around us," he said. "No-one inside the club knew. We finished brilliantly last season. We won the trophy. We knew how difficult it was.
"Jose told us the hardest season in football is the year after you win because everyone else has extra motivation. We were ready for that, but we didn’t start well and we lost control of our game, of our minds.
"For me that period of three or four months was one of the most disappointing moments in my career. Player by player, we could not deal with the pressure of what being champions of England means.
"Your opponents have big motivation and they look at you differently, they start to be scared of you.
"But when we didn’t win for six or seven games, people realised we were not as strong as last season. They could use that. And then they weren’t scared of us. This was our problem as players."
Chelsea are on an 11-game unbeaten streak in the Premier League since Guus Hiddink took temporary charge of the club and jumped into the league's top 10 with a 2-1 win over Norwich City on Tuesday.