The Hornets fell agonisingly short of automatic promotion on Saturday, going down to a late Leeds winner when a victory would have sent them into the Barclays Premier League at the expense of Hull.
Instead a semi-final meeting with sixth-placed Leicester awaits, with the first leg at the King Power Stadium on Thursday.
Watford have beaten Leicester twice this season, though, including a 2-1 away win last month.
But Hornets chief Zola said: "It will be tough. They are a team we have already faced twice and we know the quality they have. They know us, we know them. We'll go there and play our game.
"Before the game the players knew the possible scenarios. We will be ready to start again on Monday.
"The players were very tired at the end of the match, they had given everything. It's been tough but we will come back.
"The expectations have grown this season as we have grown in stature but you have to face that if you want to be a top team."
Zola is hoping goalkeeper Manuel Almunia will shake off the tight hamstring which kept him out of yesterday's match and had such a bearing on the outcome.
Jonathan Bond was drafted in to replace Almunia following the warm-up but his afternoon ended after 22 minutes when he was carried off with a broken nose.