Watford boss Quique Sanchez Flores was not happy with the Miguel Britos' red-card in the Capital One Cup defeat to Preston North End.
Britos was given his marching orders in the 75th minute with Hornets already down 1-0 in the second round fixture which was decided by Marnick Vermijl's 8th-minute goal.
After the game, Flores said: "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."