Joe Garner got the only goal of the game but the main talking point afterwards was over the red card to Wednesday's top scorer.
Forestieri received two yellow cards, the second coming for deliberate handball, but it was the first caution which provoked Carvalhal's annoyance as he felt his side should have been given a free kick at the time rather than his player be booked for diving.
"Forestieri received the ball in a good position and the defence blocked him and the referee gave him a yellow card, so the first yellow is not correct," Carvalhal said.
"The second yellow seems correct. Even though he doesn't touch the ball he's tried to put his hand on the ball and the referee therefore was correct.
"The first yellow card is unbelievable because it was a clear foul to us and he gives a yellow to Fernando. If he doesn't go down he will be in front of goal in the area with a very clear chance to score. For me he didn't dive in that moment because if he did it was not a good choice. He blocked him.
"I am happy with the attitude of our players, they tried to win the game, but we are unhappy with the score of course.
"The fans were amazing again, the game was balanced, we both created chances and in the second half we looked as though we would score but the red card changed the game. Even with 10 players we took risks and the players fought until the last second to try and win the game."