Alexis Sanchez seems set to leave Arsenal, and to a major Premier League rival at that. The only question is whether it will be to Manchester City or Manchester United.
But how often does this happen? How frequently does a top side help out another by selling them one of their best players? Does it always work out for the buyers?
Sportsmail takes a look at some of the transfers between the Premier League's top clubs over the last decade and how they worked out.
Carlos Tevez — Manchester United to Manchester City, c£47million (Summer 2009)
Probably the most controversial transfer of the lot.