Villa won the first-leg 3-1, with Watkins hitting a superb brace.
“It was massive,” the striker said. “First half, they were putting us under a lot of pressure, and they were dominating the game.
“I think we got lucky. At half-time, I said to the boys: ‘Come on, lads, we need to wake up.’
“We got lucky, they had a disallowed goal, and if that turned and it stayed 1-0, it would have been a long way back for us, because here, great atmosphere as you can see, and they were playing tough today.
“We got the goal from the set-piece, and I think that took the sting out of the game. They were dominating just before half-time, great time to score, and then we’ve come out, obviously got the second goal, and from there, we looked like we were always going to go on and score more.”
He added: “Back end of the season, I’m raring to go. I could play another 90 minutes right now.
“I’m excited for the last few games, obviously next week as well, against these. I’m hungry.
“I think their winger (Jonathan Rowe) was causing all sorts of problems tonight. Great finish, 2-1, it’s all to play for.
“So that goal at the end, I think it takes the sting out of the game, and a two-goal lead going back.”