Regis was 'saddened' to see Di Matteo depart, before offering his opinion on the successor.
"I am very saddened to see Robbie go because he did such a good job last season and had a good start to this season," Regis told the Birmingham Mail.
"But they were sliding and it's down to results these days. He will be a better manager for this experience.
"The priority now is to stay up. And the club need to think about who might be able to take them back up if they are relegated.
"It's a good job for someone."