Les Parisiens triumphed over two legs against Porto in the last 16, while the Blaugrana defeated AC Milan 4-0 at Camp Nou to overturn their 2-0 loss at San Siro in the first leg.
Ancelotti told reporters on Saturday: "We will have our chances. We will play against one of the best teams in the world, and it will be very exciting for us to prepare for this match.
"We will not be favourites, but I do not think an unbeatable team exists in football. We will do our chance to win."
Although that game will linger in the minds of Ancelotti's players, the former Chelsea boss insists that they must be focused on their Ligue 1 campaign, starting with Sunday's clash with Saint-Etienne.
"[Barcelona] are a great team with great individual qualities," he added. "On paper, Barcelona have more of a chance to reach the semi-finals, but anything is possible, and this is what makes the beauty of our sport.
"I trust and I know that in this tournament we can qualify. But today I told the players that the league championship is our main interest.
"We must remain focused and I expect to see significant effort against Saint-Etienne and in our home game against Montpellier. Then we can turns our heads to Barcelona."
Saint-Etienne have been impressive this season and sit fourth in the table, and Ancelotti praised them for their rise up the Ligue 1 standings.
"They work well because they have a very good coach, a very good tactician, who has established a good offensive and defensive organisation," he said. "They are a complete team, and we must be careful.
"We expect the match to be very complicated, because of Saint-Etienne's good string of results lately, and because they have not lost a single match since the beginning of 2013.
"But, perhaps now it is time for them to lose a few games! They are a really dangerous team, with a good dynamic.
"This Sunday, it will be a very important confrontation as Saint-Etienne are not far from us [nine points] and can enter the title race. With the game against Montpellier to come after, it will be simply a key match."
Ancelotti also confirmed that Lucas Moura, Marco Verratti and Jeremy Menez will not feature in the game this weekend.