Roma go into the round 16 tie as favourites.
"The path is long, but it's an important opportunity for us to have a great game and regain enthusiasm," said Di Francesco.
“There are only two Italian sides left in the Champions League, so we have to be ambitious.
“Porto without Marega and Corona? They have excellent replacements, Tiquinho Soares and Otavio, two important players, could play.
“Porto, beyond individuals, are a team who know what they want and are among the teams who have won the most defensive duels in the Champions League.
“That means they know what they want. It'll be an important clash."