Here's a quick look at some of the trading disasters which have occurred in recent years. Note that these are genuine foul-ups (or 'fat-fingered' trades), and not losses down to rogue traders.
Do these ratings accurately reflect each players' performances so far this season?
Tottenham Hotspur are currently in fourth place in the Premier League table.
Sol Campbell has had his say on Aston Villa's struggles.
The West Ham United player is making his loan move to Norwich City permanent.
Real Betis want Carles Gil and Villa need a new keeper.
The Blues are just outside the play-off positions in the Championship, so will be hoping that any additions can help propel them into the top six.
Sol Campbell is tipping former club Tottenham for a top four place.
The Aston Villa striker has started to find his form since arriving in the summer.
A host of Sky Sports pundits believe Tottenham will get in the top four this season.