Three goals in the dying moments of the game saw the Hornets secure a memorable victory over the reigning champions.
Speaking to Sky Sports after the win, Gracia couldn't contain his joy.
He said: "It was an unforgettable night. A great victory and a great match. I am very proud of my players today.
"You always try to look for the victory and play well. Today we played a good match, pressed high. OK, the match changed after the sending off but I think we played very well.
"Chelsea are a very big club, a big team. Today they had more difficulty because of the sending off but there was in the second half moments when they played better.
"I only think to get the next three points. Tomorrow we start training again to be ready for the next match."