Both the Blaugrana and the Blancos are safely through to the quarter-finals of this season’s competition.
Their talismanic forwards have led the charge, with Messi bagging a brace against Chelsea in the last-16 to take his goal tally to six while eternal rival Ronaldo leads the scoring charts on 12.
Both men are now members of the elite 100-goal club in the Champions League and Ancelotti, who has conquered Europe as a player and coach, believes they will prove to be the difference once again in the pursuit of continental glory.
The Italian said: “Clearly Champions League games are decided by the smallest of details and in a one-off game it is sufficient for a refereeing decision to knock someone out.
“Madrid and Barcelona are favourites for their experience and because they have Ronaldo and Messi.
“It is clear [Juventus and Roma] are not favourites because they are up against two European powers but they still will have their chances.”
Real have been paired with Serie A champions Juventus in the last eight, in what will be a repeat of last season’s final.
Barca, meanwhile, will take on Roma as they seek to break the dominance being enjoyed by their arch-rivals in Europe.
The Blancos have lifted the famous jug-eared trophy in each of the last two seasons – and three of the last four campaigns – and have their sights set on a notable hat-trick.
