In a marketing meeting room it probably sounded like good fun and something that would add to Carling's edgy, witty image engendered through years of humorous "if Carling did this" or "if Carling made that" campaigns. The trouble is that no matter how great ideas may seem, they always need to pass the test of whether there is a need for them and would the target audience engage with the message or campaign. As a football fan and a grassroots coach, I have to say this is the most bonkers idea I have ever heard of.
Where to start? Well, the campaign hinges on an assumption that if a player leaves your team you may not want to wear the shirt you bought when they arrived. As any fan will tell you, this is rarely the case. It may be a knee-jerk reaction, but very few players irk fans sufficiently to prompt a shirt to be discarded. If they have been a good player whom the club has sold there are rarely ill feelings unless they move to an arch rival. In top-flight football this is incredibly rare because clubs will invariably sell stars -- who are the big shirt sellers -- to a top club in another country so they can bank the cash and not fear playing against that athlete two or more times per season. Even if a top player goes, most are remembered fondly. My son still proudly wears his Petr Cech Chelsea shirt even though he moved to North London to play for Arsenal. My relatives still proudly wear Suarez Liverpool shirts, long after he was sold to Barcelona.
So once the initial sting is over, I'm not so sure fans are sufficiently angry at departing players to never want to wear their shirt again -- after all, it still bears the team's logo and colours. Top players will have earned a lot of money for the club and will leave fans feeling that it was great while it lasted and players sold by lower teams are typically moving up a level, which nobody can blame them for. If they're moving down a level, they're typically seeing out their career and are assumed to love the club they are leaving but are being realistic about their starting opportunities.
The ultimate problem with a shirt swap, however, is who wants to wear another team's shirt? In extreme cases the occasional fan may be so annoyed at a player for leaving that a shirt is now only fit for washing the car, with but does that mean you want to swap it for another? Come to think of it, who would want to wear your shirt bearing the name of a player they care nothing about from a club they don't follow? If they support the team of the player have moved to, they would obviously rather have the star's name on their own team's shirt. If they support neither the players old nor new team, then why would they want the shirt in the first place?
The only way this could possibly work is for teams in different countries where a fan might just want a shirt for the sake of a novelty. Half the kids I train turn up in Real Madrid or Barcelona shirts nowadays, so there is obviously interest there -- but how many such shirts will be available in a van that moves around a few UK cities during January?
Oh, and a final nail in the coffin. As in every transfer window, the big moves usually happen pretty late on, meaning the Carling shirt swap will not get the whole of January to take advantage of moving players but a day or two, at best, right at the end of the month.
So I can't see there is a demand for ditching shirts, even less demand to swap them and so, if Carling did sports marketing ideas, they would probably be non-league, from what I can fathom.