The last time Fernández Borbalán was in charge of a Real Madrid-match was when Ancelotti's side lost 4-0 to Atlético de Madrid last season, so this is definitely not an encouraging precedent for Madrid even though he was not to blame for Real's woeful performance that day.
Borbalán is not the perfect referee but considering how bad the Spanish usually are, he is probably the better candidate. Undiano Mallenco had promising potential but he made very big mistakes in recent years. It will be important for Borbalán to keep the game under control at all times given how difficult it is to officiate a Clásico between these two rivals.
Madrid will try to beat Barcelona at the Santiago Bernabéu given that Los Blancos are currently 3 points behind them after losing to Sevilla 3-2.