Personally, I don't think spending money in January by itself to help improve the back line is a vital component of fixing our problems.
Instead, it's how we play which is the problem. Jagielka, Baines and Coleman were all imperious under Moyes so the ability to defend is there.
I'm not saying go back to the days of Moyes as if they're some glorious era, but there are aspects there which could be utilised; a fair balance.
First, I'd start with being slightly more cautious in the short term to secure results and be smarter on the pitch with when and how we defend.
I'd get the defenders closer to their men, tell them to not back off as we do and practice working as unit - banks of four etc. Set pieces too as well.
Yes it may be to the disadvantage of our attacking forays, but in the short term that's a sacrifice worth making simply to find a working balance.
I am certain that Jags will help with this an awful lot, yet he isn't the magic bullet which will fix all. There were problems there prior to his injury.
His departure has just exacerbated our problems. I'd also look at what Koné and others offer defensively as their routines need sharpening.
The problem is regardless of what I would do, I'm pretty confident Martinez will not address them or at least to an acceptable level.
Personally, I would love someone like Shawcross who is gritty and nasty to toughen up our defence working alongside the charismatic Stones.
But again, Martinez would never consider such an option so it is just pointless analysis.