Flores refused to blame Miguel Britos’ red card for seeing his Hornets make an early exit at Deepdale.
“We are not pleased with the result of course but I think we had different feelings during the game,” he said.
“In the first half we kept the ball and tried to play. In the second half we had control of the midfield and were really close to the draw.
“We had two or three consecutive attempts but after the sending off it is completely different.
“I don’t like to concede goals, including early goals. We conceded a goal from an offensive throw-in. For me this is a big disappointment. We open the defence with these kind of situations.”
He added: “I think the red card was not fair. We play in England, the contact is permitted and this kind of contact is so soft it’s not a red card.
“It is maybe a second yellow card and he is sent off the same but the action is not violent. I respect the referee but he did not deserve to be sent off.
“When we had the opportunity to put Britos in the team last week, I thought it had been too long. He had lots of difficulties today, I know, but after two months it is normal.
“He said sorry. He is a good professional and he knows he made a mistake. He put his arm against the breast of the player. For that I think it is maybe a second yellow card but not a red. I think we will appeal.”