Gareth Evans says Portsmouth intend to 'batter' Sunderland at Fratton Park on Thursday night.
The Black Cats will take a narrow 1-0 lead into the second leg after Chris Maguire's superb winning goal on Saturday night.
Jack Ross' side even survived playing a quarter of the game with ten men after Alim Ozturk was shown a controversial red card for a challenge on Evans.
Portsmouth struggled to test Jon McLaughlin but Evans insisted that they are the better side, and took aim at Sunderland's full-time celebrations.
"It's still very much in the balance," Evans said.
"There wasn't much in it.
"There was a little bit of quality from them for their goal.
"They've got the goal, but it's only half-time and we said in the dressing room that we were 1-0 down half-time at Wembley.
"We went on to batter them in the second half - and that's fully what we intend to do on Thursday.
"There's still 90 minutes to play and it's not like the tie was over.
"At the end of the game they were celebrating like they'd won three or four nil," he added.
"It's up to them how they celebrate. We just need to be as professional as we can and do the business on Thursday.
"It's only 1-0 and there's still 90 minutes to play. We very much fancy ourselves.
"Perhaps mentally they feel like they've got the edge, but we feel like we've got the edge.
"It's in the balance, but at Fratton Park in front of packed crowd we fancy ourselves to score a couple of goals at least."
Fratton Park is already sold out for the return fixture and Evans says it is going to be a great occasion.
"It's going to be a great game, a great occasion and the whole of Portsmouth is looking forward to it," Evans said.
"I know the lads are extremely excited about it.
"It’s sold out and it’s going to be one of those fantastic nights at Fratton Park - and we want the result to go with it.
"We’re very positive and we feel like we’re a better team than Sunderland.
"So we have to get the result on Thursday and get the better of them."