Joe Ledley arrived after Derby conceded four goals to Bristol City in September. Since then Derby have played seven matches and conceded a total of four goals throughout, winning four and drawing three. Ledley played in all but one of these, the Birmingham draw.
I honestly forget he's playing half the time. But his impact on this team absolutely can't be denied. We defend far, far better with him playing. Davies hasn't put a foot wrong since Ledley started playing, Keogh has been much more adventurous with his ball carrying and passing and is in the form of his life, Forsyth has regained his pre-injury imperiousness (what a beast) and Huddlestone has enjoyed less defensive responsibility.
There's definite shades of Eustace during McClaren's first stint. Ledley is similarly unadventurous but does everything he does for the team, not a shred of ego on show. His selfless play allows the rest of the team to thrive. It's obvious why Wales were desperate for him to play at the World Cup despite his understandably questionable fitness.
Get him signed immediately.