Sky Sports understands that free agent Lee Naylor is on trial at Birmingham with a view to earning a contract at the Championship club.
Naylor was released by Cardiff last month after a two-year stay and the former England Under 21 international has been given a chance by new Blues boss Lee Clark to stake a claim for a deal.
The 32-year-old left-back knows the West Midlands well having played over 300 games for neighbouring Wolves before enjoying some success north of the border with Celtic.
He was on a four-man shortlist for the Scottish Footballer of the Year award in 2007 and is believed to have been close to earning a senior England cap under Steve McClaren.
But Naylor's stock has fallen since then and he played just two Championship games for Cardiff last season - the last of which, coincidentally, was a 1-0 win against Birmingham in December 2011.