"It's true... we don't know what they can do because there is a new manager and maybe they choose other players or another shape," Gracia told a news conference.
"But we know the players they have and I don't think they will change a lot the players or the way they are playing."
Under Frenchman Puel, Leicester blended a counter-attacking approach with a fluid possession game but have struggled with inconsistency this season to sit 11th in the table with 35 points from 28 matches.
They did, however, beat Brighton and Hove Albion 2-1 last time out.
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"I don't know if it's more difficult but it's different," Gracia said.
"We don't have the references we have with other coaches and other teams, but the most important thing is to be concentrated on ourselves and on our work."
Watford are eighth in the standings with 40 points.
(Reporting by Shrivathsa Sridhar in Bengaluru; Editing by Ed Osmond)
