The 23-year-old Czech striker joined the Hornets permanently from Udinese in the summer after two successful loan spells with the Hertfordshire club but is yet to feature at all this season.
After failing to even make the bench for Sunday's 0-0 draw with Southampton, Vydra's future was discussed briefly at the post-match press conference where Flores could not offer a straightforward answer.
"It is very difficult because we have a lot of players. It is not easy for me as coach, they all want to play," Flores said.
"Vydra's future could be at Watford, it could be at another team. It is impossible to know because of the club and because of the player."