It's very hard for me to push him to stay in a position that affects his familyPep Clotet.
Blues' Assistant Head Coach has been away from training this week and missed today's game at Hull City.
The Club and Head Coach Pep Clotet agreed that Herrera should be allowed to attend to personal family issues on compassionate grounds.
"Paco has had a very difficult family problem to deal with," said Clotet.
"For the last couple of months Paco tried to manage that problem as much as possible whilst being here.
"This week we agreed on him going home and trying to try and get a grip of the problem.
"I need to respect his decision because at the end of the day family comes first and he has gone there on compassionate grounds.
"The problem that he's having makes it very unlikely that he will be coming back."
"Paco has been a fantastic addition for us and he has a lot of experience," continued Clotet.
"He's helped massively with what we are doing.
"We still talk on the phone every day and I'm still discussing things with him.
"It's very hard for me to push him to stay in a position that affects his family."
The vastly experienced Herrera – 66, joined Blues to assist Clotet after he was appointed to the Head Coach’s role in June.
Clotet is also assisted by Craig Gardner, as Player/Coach, and Xavi Calm who was seconded from Blues Under-23s to add his input as well.
Everyone at Birmingham City sends their very best wishes to Paco and his family.