Nicolo Zaniolo's brace downed the Portuguese giants in Rome a fortnight ago and puts them in dire need of a win at the Estadio do Dragao.
After missing the first-leg defeat due to a thigh injury, Marega returned to action on Saturday against Benfica and he is expected to lead the Dragons' attack to ensure their progress to the quarter-finals.
Porto ended their group campaign as leaders ahead of Schalke 04, Galatasaray and Lokomotiv Moscow with a record of five wins in six matches and the 29-year-old believes the form would inspire the team's fight-back against Eusebio Di Francesco's men.
"All teams dream of being here in the last 16 of the Champions League," Marega told Uefa website.
"We are one of the 16 best teams in Europe and we just have to be motivated for this challenge. I think we will be prepared and we will do our utmost to help Porto.
"We were very proud of this triumph [winning UCL Group D], it was a great motivation. We feel good for beating Porto's record in the Champions League group stage and for winning the group.
"It was another stimulus for the round of 16 and I think it will also help us prepare the decisive game more calmly.
"We only lost one game in the Champions League and we are determined to continue in the competition."
Despite the injury setback, Marega is having an intriguing season with Porto having broken his Uefa Champions League duck and also matched club legend Mario Jardel's scoring record of five goals in five matches in a row.
Marega opened his goal account in the elite European competition against Galatasaray to give Porto a 1-0 win back in October and he has described the moment as the 'greatest satisfaction' in his career.
"It's a great feeling, I had a special pleasure when I scored my first goal in the Champions League against Galatasaray," he continued.
"It was the moment of greatest personal satisfaction in my career. At the moment I have five goals and it's great, I'm very happy.
"Last year I was not well in the Champions League, I did not score any goals, so I feel very good to have scored five times this season.
"As for the record, we'll see it at the end of the season, but the most important thing is for the team to win."
Following his move to the Estadio do Dragao from Maritimo in 2016, the Malian forward struggled for playing time in his first year at the club which saw him join Vitoria Guimaraes on loan for the 2016-17 campaign.
But Sergio Conceicao's appointment in 2017 has made him become a prominent member in Porto's squad returning 29 league goals in 48 matches so far.
"He [Conceicao] bet everything on me and it was thanks to him that I made the best time of my career," he noted.
"I am very grateful to him for this. He knows how to deal with me and how to get the best out of me on the pitch. He's really a great coach."