"We did try for Jan Koller, we showed our ambition and intention there," Blues boss Alex McLeish told the Birmingham Mail.
"But he chose a massive offer in Russia, which we couldn't compete with.
"There was no doubt we would never have got Koller five, six years ago. We would never have attempted to.
"It's only now that he's in the twilight of his career that a club like ours, where we are at the moment, could offer him something.
"We actually made the approach before the European Championships. They wanted to wait until it was over and, to be fair to the big fella, he had a half-decent tournament.
"He scored a goal and caused Turkey no end of problems in the game they came back sensationally to win. We just felt that we needed something different up front, and he was available.
"We know that Garry O'Connor is a big presence but he's slightly different, quite a technical player. He's good with both feet and half-decent in the air.
"Koller maybe would have allowed us to get up the pitch and support, and caused a lot of trouble with his size and physique."