The 26-year-old completed a season-long loan move on deadline day.
Herrera said: "I'm pleased because Javier has gone to one of the most important clubs in the world.
"Before he was at United and now his arrival at Real Madrid is phenomenal.
"I think that he will see a lot more action with his new club. There is no striker like him."
Herrera added: "Not anybody can score as many goals in the Premier League from so few minutes as he did. He always does his job."
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