Eliaquim Mangala's diving header gave the Portuguese outfit a 1-0 lead following the first leg at the Estadio Do Dragao, leaving the tie in the balance ahead of the return fixture in Seville on Thursday.
Pareja, who joined Sevilla on loan from Spartak Moscow at the start of the season, believes his side have every chance of progressing to the last four.
"The tie is wide open," he told the club's official website. "Porto have done well in the Champions League and the Europa League, but with all due respect, we want to get through and we will throw everything at them.
"We have to do more than just pressurise them, we have to enjoy ourselves because we suffered at the start of the season and now is a time to have fun, just as much as the fans will, we want to taste every minute.
"When our lot sing and inspire us, they give us a nudge which means we produce more than we normally could."
Porto will be without two key players for Thursday's game, with striker Jackson Martinez and midfielder Fernando both missing through suspension, but Pareja has told his team-mates to remain wary.
"We could comment that they are a weaker team without Fernando because he brings the balance between the defence and attack," he added.
"However, they have many quality individuals who can fill in for him."
Sevilla head into the game on the back of a 4-1 thumping of Espanyol on Sunday and Pareja paid tribute to the job Unai Emery has done in leading the side to fifth in La Liga, still in with a chance of UEFA Champions League qualification.
"It's really easy to fall back when you are doing well, but you have to carry on pushing and this makes every day fun and you also strive to do things well," he said.
"This is shown in each training session and also Emery is very positive, he is always behind us and that makes us optimistic."
