Glenn has called for the players to show character and be brave ahead of the clash with Chelsea at Stamford Bridge.
A cup defeat to the same opponents is not the ideal preparation for an away Premiership match and Glenn says the hurt felt after the cup game has got to be overcome.
"It calls for a big lift in character," said Glenn. "We've got to show a lot of it, we've got to be brave.
"Obviously it hurt us the other night, big time, the way we lost. The four goals we feel we gave them made it uphill for us.
"So yes, it's a tough game, anyone going to Chelsea gets a tough game, we know that - London derbies always are.
"We know we're in for a tough game and we've got to respond and it's how we respond and show the will to win and the will to go over there and get a good result that's important."
Glenn adds that he hopes a lesson has been learned from Sunday, where he suggested that the players might have been a bit too hyped up.
"I'm hoping we've learned a lesson. We've got to go there and compete and that's no different from the other night. We've got to make sure we get the ball down and play as well.
"If we can go across there and get a clean sheet I'm sure we can do well."