The draw keeps Watford unbeaten upon their return to the Premier League, with three draws to their name since promotion from the Championship.
Club-record summer signing Etienne Capoue had a gilt-edged chance to break the deadlock late on for the Hornets, but the midfielder squandered the opportunity from close range.
“We tried to win but it was impossible,” he told reporters post-match. “They changed their plan and it was difficult.
“We had maybe two or three chances. It was difficult to create opportunities because they played well and defended with five players.
“We try to be positive. We’re in a good position in the table and we’re unbeaten heading into our next match.
“It’s not the best match we play, but in terms of the attitude and the passion of the players, I’m very happy.
“We try to keep the balance always between defence and attack. We are keeping clean sheets but it’s important for the confidence of the players.”
Despite making 11 new signings in this transfer window alone, Flores spoke of his desire to add more faces in the last week of the transfer window.
“We are in the last week and we’re working very hard to try and incorporate a couple players more.