The Galician outfit are at the Santiago Bernabeu on Saturday for their La Liga clash against the defending Spanish champions.
"This is the best Real Madrid team in history," said Herrera. "Last year they were the topscorers, they beat you by knockout. This year they have started differently but they are recovering their style.
Celta are currently 12th in the league standings with nine points from seven matches, just three points above the relegation zone.