The Colombian has been in fine form this season, and has been linked with a host of clubs across Europe, inlcuding the Spanish champions.
The Galicians go up against Diego Simeone's side on Friday, and Herrera is in no doubt as to who his side will have to keep quiet.
"Falcao is now the world's best pure No.9. Another striker who I also love is Benzema, although he's perhaps not an 'old-fashioned' striker," he told reporters at a press conference.
"He does not have a finisher's brain like Falcao does. We'll have to do very well to defend against him because in the area he is a phenomenon."
Falcao has enjoyed an excellent start to his Liga campaign, scoring 17 goals in 15 games.