Racing are the surprise name in the final eight of the competition, with the former La Liga side eliminating the likes of Sevilla and Almeria on their way to this stage.
Fernandez's side, who currently top their domestic division, travel to Sociedad for the first leg on Wednesday.
"We'll compete and we'll fight for it. If we don't get it, we've already done more than we thought we would, but we have to keep going until we exhaust all our chances," Fernandez told reporters.
The return leg at El Sardinero will take place next week.