Brentford are currently in a play-off place but were well beaten at Roots Hall at the weekend.
Boss Allen told his club's website: "We were outfought, outrun, outjumped and never won enough possession to pass and play.
"Away from home we have been dominant in all these areas.
"Thankfully on Tuesday night we have another game to put things right...those players selected must be ready to respond in the right way."