Everybody at some point in their life will have their 'go-to' shop where they know they're going to find what they're looking for.
It seems that it's the same case with football clubs, with teams often doing business with each other again and again until it seems like they're actually affiliated with each other.
Whether they become jokingly labelled as a feeder team, or the clubs just seem to like doing business, they can usually be banked on to buy or sell with each other every year or so.
Here's a list of seven pairs of clubs who seem to always do business together...
1. Manchester United & Everton
This partnership usually works more in Everton's favour than United's, as the blue half of Merseyside always seem to snap up United's fringe players, whilst United are usually first in line to take Everton's star players into the upper echelon of the Premier League.
Their 'partnership' is one of the more frequently seen pairings in recent years, with Wayne Rooney and Romelu Lukaku swapping places (give or take £75m) last summer.
Notable Transfers:
Tim Howard (MUN to EVE, 2006); Morgan Schneiderlin (MUN to EVE 2017); Marouane Fellaini (EVE to MUN 2013); Wayne Rooney (EVE to MUN 2004 & MUN to EVE 2017)
2. Liverpool & Barcelona
Very much in Barcelona's favour, Liverpool's star players always seem to end up at the Camp Nou sooner or later once the Catalan giants come a-knocking.
However, Liverpool have taken the odd gem from Barcelona in the past, so it's not completely one-way traffic, but Liverpool fans have grown to learn that a looming Barcelona never bodes well.
Notable Transfers:
Philippe Coutinho (LFC to FCB 2018); Luis Suarez (LFC to FCB 2014); Jari Litmanen (FCB to LFC 2001); Luis Garcia (FCB to LFC 2004); Javier Mascherano (LFC to FCB 2010)
3. Bayern Munich & Borussia Dortmund
Transfers between Bayern Munich and Borussia Dortmund usually follow the same formula:
1. Bayern sell a fringe player to Dortmund.
2. That player then becomes a lot better at Dortmund.
3. Bayern then buy him back several years later.
4. Rinse and repeat.
But the teams have always had dealings together, with players such as Torsten Frings and Michael Rummenigge making moves before the big money started to come into play.
Notable Transfers:
Robert Lewandowski (BVB to FCB 2014); Mario Gotze (BVB to FCB 2013 & FCB to BVB 2016); Michael Rummenigge (FCB to BVB 1998); Torsten Frings (BVB to FCB 2004)
4. Arsenal & Manchester City
Over a period of five years, Manchester City took five of Arsenal's best players to the Etihad stadium with their newfound wealth. Coincidentally, none of those five players are still at the club.
Every player who made that move became instantly outlawed by the Arsenal fans and had Alexis Sanchez gone to Manchester City instead of United, he would've followed exactly the same path.
An even stranger statistic is that Arsenal haven't bought anyone from Manchester City for almost 35 years, with their most recent being Tommy Caton's £575,000 transfer.
Notable Transfers:
Emmanuel Adebayor (ARS to MNC 2009); Kolo Toure (ARS to MNC 2009); David Seaman (ARS to MNC 2003); Gael Clichy (ARS to MNC 2011); Tommy Caton (MNC to ARS 1984)
5. Liverpool & Southampton
Another unfortunate 'feeder team' scenario here, very much on everyone's minds following Virgil van Dijk's record £75m transfer in the recent January transfer window.
During the 2014/15 season the Reds poached three players from the Saints, before taking one more player each season after that point.
Much like Arsenal and Man City, there haven't been a lot of transfers going in the opposite direction, with the most recent being Adam Hammill (me neither) who went on loan to Southampton in the summer of 2007.
Notable Transfers:
Virgil van Dijk (SFC to LFC 2018); Sadio Mane (SFC to LFC 2016); Nathaniel Clyne (SFC to LFC 2015); Peter Crouch (SFC to LFC 2005)
6. Real Madrid & Juventus
With the prestige of these two teams, everything related to them regarding transfers is going to be of the highest class.
They may not be in business as frequently as Liverpool and Southampton, but the transfer dealings between these two always become one of the defining deals of that window and sometimes involve era-defining players.
Notable Transfers:
Alvaro Morata (RMD to JUV 2014 / JUV to RMD 2016); Sami Khedira (RMD to JUV 2015); Fabio Cannavaro (JUV to RMD 2006 / RMD to JUV 2009); Zinedine Zidane (JUV to RMD 2001)
7. Arsenal & Chelsea
Over the years, many players have crossed London in a transfer deal, but the more notable transfers usually got through these two clubs.
Whilst they don't happen as regularly as some of the other pairs on this list they are always big transfers, which is strange considering the rivalry between the two sides.
But with a proper rivalry comes respect for the opponent and there's no doubt that the clubs respect each other, even if the fans don't...
Notable Transfers:
Olivier Giroud (ARS to CHE 2018); Petr Cech (CHE to ARS 2015); Yossi Benayoun (CHE to ARS 2011); (Ashley Cole (ARS to CHE) & William Gallas (CHE to ARS) Swap Deal 2006)
- 90Min