Making the wrong decision in the transfer market in January can have hugely negative effects for a team's season.
We have already covered the top 10 signings in the history of the winter window, but how about the flops and failures who arrived with a reputation only to completely combust?
Sportsmail has put together a guide to the worst January arrivals ever.
Arsenal were in the midst of an actual, genuine bonafide title challenge. They were top of the league.