A 2-0 victory over Brighton & Hove Albion secured Tottenham's place in the quarter-finals, and Vertonghen has quickly turned his attention to going on a winning run in the league following Sunday's defeat to Newcastle United at White Hart Lane.
"Hopefully we can get back on track now. We are doing well in the cup but we need a run of a couple of games where we are doing well," the Belgian defender told reporters.
"What is missing? It's difficult to say. We are working very hard and we believe in each other - we are getting close to what we want.
"The fans have the right to expect things from us as players. We want to do well and they expect us to do well - they have expectations like we do."
Spurs, who meet Aston Villa on Sunday afternoon, have won just three of their nine league games this season.