Benitez revealed former Bolton man Cahill is currently suffering from a virus, while Spain international Azpilicueta has a leg problem.
|CHELSEA TO EASE PAST BORO?|
|16/1||Chelsea are 16/1 with PaddyPower to beat Middlesbrough 4-0 in the FA Cup|
Chelsea reached the fifth round after overcoming fellow Premier League side Southampton and League One outfit Brentford, but only at the second attempt.
Should Chelsea win at the Riverside Stadium against their Championship opponents, they will take on Premier League leaders Manchester United at Old Trafford for a semi-final berth.