The club will not comment on the fee payable to the Tyke's.
Barker is a natural left back and has played over 120 games at Div 1 level.
He will complete stage 2 of Lennie's jigsaw. A left sided midfielder (Whalley) was stage 1. Barker (a left sided defender) is stage 2. The third and possibly final stage is a back up goal keeper to Neil Alexander.
With City alreeady hot favourites for winning the division these new signings could shorten the odds even further.