Despite only conceding 17 Premier League goals this season, the Blues have had their fair share of defensive woes with captain John Terry out with a knee injury and David Luiz struggling for form.
However, with the Brazilian being moved into a defensive midfield position and the Serbia and England internationals forming a strong bond, the Stamford Bridge interim manager thinks the hard work in training is paying off.
|PREMIER LEAGUE LATEST
|8/1||Chelsea are 8/1 with William Hill to beat Everton 2-1
"Since I arrived, we have been working with different defenders. The team is strong in defence and we have the balance because we can still attack.
"It is a question of spending hours on the pitch and on the training ground. You can see the difference [with Ivanovic and Cahill]."
The duo will have a stern test against sixth-placed Everton on Sunday afternoon, as the Toffees can rise above Chelsea into third place with a win at Goodison Park, pushing Chelsea out of the top four in the process.
The Champions League holders were knocked out of Europe in the group stages this season, and are currently 14 points behind Premier League leaders Manchester United, albeit with two games in hand.