Redknapp took over at St Andrew's at the end of last season, saving them from relegation to League One before overseeing a summer of transition, with 14 new players joining the club.
The axe fell after a disastrous start to the new campaign, however, with just four points garnered from their opening eight games, a run only slightly better than that of bottom-placed Bolton Wanderers.
Rowett was in charge at Birmingham last season and had guided them to within a whisker of the playoff places when the axe suddenly fell just before Christmas, a shock decision that backfired as Rowett's replacement Gianfranco Zola then just managed two wins from his 24 games in charge.
"If you have signed 14 players, you would think you would be given more time," Rowett, who has been in charge at Derby since March, said of Redknapp. "But I've been on the receiving end, so nothing shocks me anymore.
"I am Derby County manager now, so what Birmingham do is up to them – but it is sad to see. They have probably doubled or trebled their budget in the past year but not won many games.
"I'm sure the fans are disappointed and I'm sure the people at the club are, too. The reality is that they have gone from seventh and challenging to down by the bottom and surviving.
"I wish them well and hope they can pick up. They are a great club and have a fantastic fan base – but of course my main focus is on Derby County."
Rowett welcomes his former side to Pride Park in the Championship tomorrow afternoon.