Boss Gianfranco Zola was left to rue a lack of a cutting edge as the Hornets were stung 1-0 at the King Power Stadium on Thursday.
Leading scorer Deeney is back after a one-game suspension following his dismissal in the last-day drama against Leeds and his return makes Zola confident of progressing.
He said: "I'm sure we can do it. I am confident because we have goals in our side and we will have Troy Deeney back from suspension.
"I will have different options on Sunday, I'll [evaluate] all the players and will find the best solution."
Matej Vydra has failed to score in his last 12 league matches but could still partner Deeney in attack.
Leicester boss Nigel Pearson, meanwhile, reported no injury problems following Thursday night's clash and could name an unchanged starting line-up for the third straight match.
Paul Konchesky returned from a minor hernia operation and was on the bench for the first leg. A possible change could see him recalled at left-back at the expense of Jeff Schlupp.
Ritchie De Laet (calf) came through the clash unscathed and will keep his place. Loan duo Michael Keane and Harry Kane are free to play in the play-offs.