If you would kindly cast your minds back to this year's January transfer window, many eyebrows were raised when Manchester United - a team struggling badly even to keep in touch with the top four after the departure of Sir Alex Ferguson - managed to sign Juan Mata from title-chasing Chelsea.
The Red Devils' status as one of the biggest and most reputable clubs in world football meant that their successful efforts to sign a top-class footballer even when enduring such a difficult spell was not a particular shock.
However, what was a surprise was that Chelsea - who have been fighting tooth-and-nail with Manchester United for domestic supremacy for a number of years now - allowed one of their most-prized assets to join a fierce rival.
The history of the Premier League is littered with several examples of these sorts of moves between rival teams, with many - most notably former England defender Sol Campbell's switch from Tottenham to Arsenal - understandably creating huge controversy and ill feeling.
With the next summer window now quickly approaching on the horizon, GMS have noticed a number of rumours concerning potential transfers of this nature beginning to seriously gather pace over recent weeks and months.
Here, we take a little look at eight of those rumours and decide just whether or not we think they stand a chance of happening.
Click on the tabs to get going and, as ever, don't forget to leave your thoughts in the comment box provided below.
What do you make of such rumours? Do you see any of these deals actually coming off or are they nothing but pure fantasy?
Do you agree with our take or have any suggestions for other speculation that could be added to the list?
Let us know!