A stoppage time goal from Trezeguet sealed a 2-1 win over Leicester City at Villa Park on Tuesday.
Speaking after the game, Grealish said: "It shows what character we've got in the team. We were in a sticky patch before Christmas – we couldn't string four passes together, never mind winning, but we have started the new year in great form.
"This is massive. It's my fifth or sixth time at Wembley with Aston Villa which I'm over the moon at. I love a trip to Wembley. We're looking forward to it.
"In the first leg we were under so much pressure but today we were brilliant and had the better chances if anything.
"The keeper was great. Everyone was brilliant. Now we'll concerate on Saturday and try to get ouf of the bottom five."