Spain international Fabregas has missed Chelsea's past two matches against Manchester City and Aston Villa, after coming off in the League Cup semi-final second-leg clash against Liverpool earlier this month.
The former Barcelona midfielder was expected to come into contention for Saturday's trip to Villa Park, which Chelsea won 2-1.
However, Mourinho opted not to throw Fabregas into action as a precautionary measure.
"I think Fabregas plays on Wednesday because against Villa the decision was to protect him." Mourinho said.
"I didn't want to risk two players at the same time because Willian had a minor problem from the previous game and was also a risk. So to start two players with a risk was a big gamble. So we gambled with one.
"We didn't miss Cesc against Aston Villa because Ramires is back and the best of Ramires is back too. He was great against Liverpool, Manchester City and Aston Villa. He has a different profile of play to Cesc, but he gives a lot."
Fabregas has proved a hit at Stamford Bridge since signing in a big-money move from Barcelona in the close-season.
The Spaniard has contributed 15 assists and two goals in 21 Premier League appearances.
