I hear what Boz says re centre of defence being weak link, although I think the whole defence is fragile and full back positions could be a route cause. In Horwood we have a full back who does look capable going forward with decent distribution, but cannot defend. Wingers are going past him with too much ease and even get time to get heads up and pick out a pass. At a different level of course, but there are other international full backs with the same attributes eg Glenn Johnson -and I guess Ronnie knew what he was getting when he sigend Horwood and maybe was going for a more offensive game plan, which for various reasons including injuries etc he cannot implement. So we end up having to defend more with defenders who are will struggle. Only solutions are, if we are to remain on the back foot alot during games is to move him out and look for basic solid defenders or set up a system to provide protection and ensure the players in front of the full backs do their bit.
It might be expedient, given the lack of funds and priorities elswhere in the team, to kiss and make up with Holmes and see if he can get remotivated - thus releasing Hately for the defensive midfield role.