The vastly experienced former Champions League winner was appointed by Clotet as his Assistant Head Coach.
And Herrera, who was Rafa Benitez’s assistant when Liverpool won the famous 2005 Final against AC Milan, already believes Blues players are much better than they may actually think they are themselves.
Herrera has now enjoyed a week’s worth of coaching the squad.
Speaking to bcfc.com at the Club’s pre-season training camp in Portugal, Herrera said: “I am very happy to be here.
“I like to help build a new team, and this is the case for Josep. He is my friend and I enjoy working with him.
“And I’m also very happy because I think Birmingham is a good club and Birmingham is a nice city.”
“The first day, the players are looking at me ‘what is this?” smiled Herrera. “That is understandable.
“But now, always they have a joke we me and I have integrated very well.
“They are good people, which is important, and good players.”
Herrera continued: “Josep is working very hard, working a lot. He needs a little time; that is important.
“We need at least two or three players more to complete the team, perhaps.
“And at the moment, in my opinion, the team is at 50 per cent (at the moment) because these players are much better than they actually realise.
“Working every day, thinking every day, coaching . . . we will try to help them reach their best.”
Herrera has coached two clubs to promotion to Spain’s top-flight. And, as sporting director, he installed Ernesto Valverde as coach at Espanyol, who then reached the 2007 UEFA Cup Final.
Clotet described himself as ‘honoured’ that the 65-year-old fellow native of Barcelona agreed to throw in his lot with him at Blues.
Herrera said: “Me also! It’s the same.
“I have known Josep from a long time before.
“I have seen a lot of things in football. And if I can use them to help him – he is a very good manager, a very good coach – I will be delighted.
“If I can support him in the small things, too, then I will be happy also.
“We share the same ideas, more or less. Sometimes it’s normal that I may prefer one thing and he may prefer something else.
“But he is the boss.
“It is good to be like that. We talk all the time about football, ideas.
“Two different opinions, but it is good to have that. He might use my advice, my ideas, he might use his own.
“We have lots of discussions and the way we work together is nothing unusual.”
Herrera understands what Blues have built as their strengths in recent times and appreciates the need for evolution, not revolution.
“Normally I’d take my experiences of Spain and translate them into the team.
“Maybe it is 90 per cent the English idea and I want to complement that with 10 per cent Spanish ideas.”