Birmingham boss Chris Hughton took Newcastle to the Championship title just two years ago, but feels the division has become even tougher since then.
The Blues are currently four points off the play-offs and 10 adrift of the automatic promotion places with three games in hand.
Hughton told the Birmingham Mail: "I am talking about only two years, to when I was at Newcastle, and I think the Championship is more competitive than it has ever been. When you look at Doncaster beating Ipswich and Bristol City, who were bottom, on a run of three games without a loss, taking seven points from nine, that shows you."
He added: "I honestly believe that on any day any of the teams at the bottom are capable of beating those at the top. Probably at this moment Southampton are the side showing the most, hence their position in the league, and they look very, very strong, as do West Ham. I think perhaps outside of that anybody can beat anybody."