Birmingham have completed the signing of experienced midfielder Hayden Mullins from Portsmouth on a two-year contract.
The former Crystal Palace and West Ham player was expected to leave Fratton Park this summer due to their financial woes and spent the latter half of last season on loan with Reading.
Mullins, who can also operate at right-back, helped the Royals secure promotion to the Premier League and will hope to repeat that feat under Lee Clark at St Andrew's.
The 33-year-old becomes the third player to join Blues in recent days following the arrivals of forward Peter Lovenkrands and back-up goalkeeper David Lucas.
Meanwhile, Clark has appointed John Vaughan as the club's new goalkeeping coach following the departure of Dave Watson to Norwich.
Clark has turned to former employers Huddersfield for the services of Vaughan, 48, who had been with the Terriers since 2005.
Vaughan enjoyed an 18-year playing career, which included spells with West Ham, Fulham and Cambridge, before hanging up his gloves in 2000 at Colchester.
Watson, who left Birmingham last week to team back up with former Blues boss Chris Hughton at Norwich, played a big role in the development of Joe Hart, Ben Foster and emerging talent Jack Butland during their time at St Andrew's, earning international recognition as he joined England's backroom staff at Euro 2012.