Spain star Fabregas came off during the Blues' League Cup semi-final victory over Liverpool with a hamstring injury and missed the draw with Manchester City and Saturday's win at Aston Villa.
But Mourinho confirmed Fabregas will be back in midfield for the showdown at Stamford Bridge as the Blues aim to maintain their seven-point lead over City at the top of the table.
"I think he (Fabregas) plays Wednesday because on Saturday it was a decision to protect him," Mourinho said.
"We didn't want to risk two players at the same time. We risked with Willian and to start two players with a risk is a big gamble and we gambled with only one."
In the absence of Fabregas, Ramires had been selected in midfield, alongside Nemanja Matic, following his own return to full fitness and Mourinho admitted it was a great help to have such quality back-up.
"The best Ramires is back and the best Ramires played against Liverpool, Man City and Aston Villa," Mourinho added.
"He is a different profile of player (compared with Fabregas) but he is a fantastic player for us." Mourinho also hailed Branislav Ivanovic following his superb winning goal in the 2-1 success at Villa.
"Every striker in the world would be proud to score that magnificent goal," he added.
"For a right-back whose left foot is not his best one it is an amazing goal, especially when it is the winning goal. If you score that goal and it is 3-0 or 4-0 it is a different thing.
"I am very happy because he is a great guy and what he is doing for us is unbelievable with the foot injury he had against Liverpool when he played the rest of the game, and he played against Man City and Aston Villa.
"He is one of the best signings. He came immediately after I left Chelsea and after that he made a fantastic contribution for this club."
'We can use that game to change the result'
Everton have not won in the league at Stamford Bridge since November 1994, but defender Bryan Oviedo believes Roberto Martinez's side can defy recent history and end that barren run.
One win in eight league games doesn't suggest an upset is on the cards with Everton 12th in the table and only seven points above the relegation places.
But the Toffees' only defeat in their last six games was a penalty shoot-out FA Cup exit at West Ham and they head to London after drawing 0-0 with Merseyside rivals Liverpool last Saturday thanks to a third successive clean sheet in the league.
Oviedo played his part in recording that after filling in at left-back in place of Leighton Baines, who is again doubtful with a knee injury, and the Costa Rican international is looking to erase his disappointment at not beating Liverpool by slowing Chelsea's title charge.
"We can use that game to change the result. It will be a very good game against Chelsea and we have a big opportunity to pick up a win against them," he said.
"We need to keep progressing and we need to continue to build. It's good because we have a game on Wednesday which is a chance to do so.
"The most important thing for us is to go to Stamford Bridge and win points. "We feel confident and we want to continue like that. We know it is going to be a very difficult game because Chelsea are the best team in the league at the moment.
"But we need to work hard and concentrate on a very important game."