Jake Bidwell will remain on loan at Brentford for a further month.
The left-back, 19, joined the Bees in August on an initial one-month deal which has since been extended several times.
He will now remain in west London until early February.
The Blues academy graduate has now played 27 times for the League One outfit, becoming one of the first names on the teamsheet and helping them progress to fourth in the table.
Bidwell was permitted to play in the FA Cup by Everton and should Brentford beat Southend in a third round replay, they will host current holders Chelsea later this month.