Costa is apparently unsettled by an offer from the Chinese Super League, Blues manager Antonio Conte asserting the Spain international is battling a back injury.

He was left out of the squad as the Premier League leader eased past Leicester City 3-0.

Courtois feels Conte's men proved a point in bouncing back from their loss to second-placed Tottenham.

"Of course we have enough quality to replace Diego," the Belgiun said. "Diego is important for us but if he's not there for one game we know we can handle it as well.

"Was this a message to our rivals? Yes, just to see Chelsea won 3-0 and that loss at Spurs didn't affect us and we can play without Diego if need be. I think everybody hoped for us to drop points and we didn't so that was very good."

Chelsea is seven points clear at the top, with Spurs and Liverpool its nearest challenger.

Despite being top, Courtois insists there is more pressure on those teams chasing Chelsea.

"Obviously if you are in front you have the pressure of wanting to keep that gap," he said. "But for us we are there, we are clear at the top and the pressure is more on the other teams than on us."