Birmingham are interested in Bristol City defender Aden Flint.
The 28-year-old is on Harry Redknapp's list of targets, accroding to PA Sport.
Birmingham are yet to make a bid but Redknapp does want to add another defender, having lost out on John Terry to rivals Aston Villa.
Flint signed a new deal at Ashton Gate until 2020 in December and the Robins want to keep him.
Flint has made 200 appearances for Bristol City, scoring 29 goals, since joining from Swindon in 2013.
He netted five times in 53 games as Lee Johnson's side finished 17th in the Sky Bet Championship last term.
Birmingham have already signed centre-back Marc Roberts from Barnsley and goalkeeper David Stockdale on a free transfer after he left Brighton.
Middlesbrough winger Stewart Downing is also a target with Robbie Keane, who worked with Redknapp at Tottenham, also an option.
Birmingham have already had a bid for Preston striker Jordan Hugill, who scored 13 goals last season, rejected.