Deulofeu netted his second of the game in extra time, completing a remarkable comeback at Wembley and booking a final showdown against Manchester City next month.
Goals from Matt Doherty and Raul Jimenez meant Wolves were 2-0 up by the time the former Barcelona winger was introduced from the bench midway through the second half and he reduced the arrears with a sumptuous chip in the 79th minute.
Watford captain Troy Deeney won and converted a penalty deep into stoppage time, leaving the livewire Deulofeu to finish off a crestfallen Wolves.
"In that moment, I think he was angry when he started to play," Gracia told a post-match news conference.
"But I like to see my player this way, with that attitude. He felt angry in this moment, to show what he is able to do and he helped the team by scoring two important goals.
"The first one is high quality but it is not a surprise for me because I see him in all the training sessions.
"He always accepts the decisions and he knows in other moments there will be other players in the same situation.
"I suppose he will be angry in that moment because he wanted to play the semi-final. He has played almost all the games before and he wanted to help the team. He has done it.
"We knew before the game when we started with other players that Gerard would be important during the game. I knew it, with more spaces. What I didn't know is we would be losing 2-0."
While that aspect came as a surprise to Gracia, he had no doubts over Deeney's capacity to step forward in a high-pressure moment.
"Troy is our captain and is important on the pitch and out of the pitch as well," he said.
"In that moment, to be honest, I was full of confidence. I was calm because I knew Troy would score the second goal."
Gracia spoke after a brief appearance in the media room from Wolves boss Nuno Espirito Santo, his opposite number who still looked somewhat shell-shocked by what had unfolded.
"These are very tough moments of real pain and disappointment.
"The feeling that we have is that we had it and it went away from us. We have to look at it. We have to realise the last minutes of the game we should manage better."