Fabregas has been relegated to the bench after N'Golo Kante's arrival from Leicester last summer.
But Wenger says the former Gunners captain is still a big player for Antonio Conte.
"I know well Fabregas - he’s on the bench but he’s a huge player," Wenger said.
"To keep him out of the side, Matic and Kante they have done a huge job.
"Overall those two play a big part."
Wenger says his side need to attack at Stamford Bridge to get anything out of today's game.
"We have to play with real belief and drive because that’s our main quality today," he added.
"Our players are offensive, so we need to express that."
