I know there's rumours about Twaddle doing the rounds but if you put that to one side I think it'll be difficult getting a suitable replacement for Paddy. The very reason Boyle is likely to move on is there's always a shortage of decent left sided defenders, which in turn means replacing him more difficult. Factor in McNamara appears to favour a more fluid formation and we no doubt need a left back that's comfortable going forward.
As said previously I don't believe a return for Kevin McKinlay, provided he can prove his fitness, would be a bad move.