Assuming he is on a cheap deal. I'm not even sure what a cheap deal is any more to be honest.
If he's in the lower half of the earners at the club, has been promised a decent contract if he performs and if he doesn't we can ship him out at the end of the season then there's comparatively very little risk.
But if he's in any way talked his way into a decent wage and that stops us getting in a body in a position we are actually short then it's a bad bit of business.
Weirdly the fact that he was once a talent, only 27, twice capped for England, had a couple of (at the time) big-ish money transfers makes it kind of seem worse because the media will talk it up like its a marquee signing for us, rather than the cheap gamble we have to hope it is. I'm sure there have been players who have essentially fallen out with a club and been transformed after a transfer. Not sure I can think of many though...