Mo Diame's stunning second half strike gave Hull a deserved 1-0 win at Wembley to take them back to the Premier League at the first attempt and inflict heartbreak on Wednesday.
And Carvalhal said his side were not at their best on a difficult afternoon at the national stadium.
"I think Hull City deserved to win this game," he said.
"They were better than us in the 90 minutes.
"We tried to do our best, we tried to play our football.
"But we did not play today like we usually play. We play better than this during the season.
"In the defensive part of the team with the organisation, I think we did well all the game.
"In the first half, our midfielders came to the ball too much and because of this, we opened a big gap between the midfield and attack.
"In the second half, we corrected this. We started moving the midfielders in different lines, we linked the game better and started to play a little more in the offensive part of the pitch."
Diame struck a powerful curling effort into the top corner, finally beating Keiren Westwood who had denied Hull on multiple occasions with superb saves.
Carvalhal said: "Hull City are a strong team when they win the ball, they go fast to the counterattack and in one of these situations they scored a fantastic goal.
"I thought this game would be decided in this kind of situation."