Leicester come up against former boss Claudio Ranieri at Craven Cottage on Wednesday and Puel believes he may have to do without the England global. I don't know for the moment.
"I can not say the player with the problem but I can not know my starting players in two days".
"People have been questioning why we are taking 2 banners to Leicester tomorrow that are not #Watford related".
Asked if Vardy may need an operation, Puel said: "I don't know". He (Vardy) felt something and we will discuss with the medical staff. It is a balance to know his feeling.
"Tomorrow will be another day, it will be for Jamie and for all the other players that feel something [an injury]".
"It's an important game and I hope the other players will be ready in their minds to play and replace another team-mate".
The hosts are unbeaten in five league games, their best run for a year, while Watford have only collected one point from four games - not a sequence that will please Javi Gracia, who signed a new long-term contract earlier this week.
If Leicester continue at this rate, they may end up breaking the record for sending offs in a Premier League season.
The Italian won a shock title with Leicester in 2016 and Puel knows the qualities Ranieri has. The veteran keeper conceded from Leicester's only two shots on target, and his 12th-minute faux pas bringing down the striker was the last thing Watford needed when goals are proving so hard to come by in recent weeks.
"We need to be aware and be careful of this team because they play very well".