Birmingham completed the signing of the striker in a £6million deal from Valencia on Wednesday.
“In Switzerland we met with a representative of Manchester City. We wanted to hear his plans before we met with Birmingham,” Zigic’s agent Milan Calasan told the Birmingham Mail.
“They introduced into the game the eventual sale of (Emmanuel) Adebayor so it was immediately clear that everything was long term, so it was no surprise we automatically withdrew from everything.
“Then we were contacted by Aston Villa on the day Nikola had already arrived in Birmingham.
“They begged us to wait a while. Without Martin O’Neill, no decision can be taken and he is on holiday.
“In that case, there was nothing more logical than to finish a job with the club where all the doors were open (Birmingham).
“We had a great welcome from Birmingham. Alex McLeish (Birmingham) spent an hour chatting in the hotel to Nikola.”