Alexis Sanchez was on his way to Old Trafford, with Henrikh Mkhitaryan travelling in the opposite way to London.
Sanchez - one of the Premier League's finest at the time - was desperate to leave the Gunners to try and win the Premier League under Jose Mourinho.
As for Mkhitaryan, he was a talented player who needed a fresh start in Arsene Wenger's exciting attacking lineup.
All good, right? Oh how wrong we all were. Fast-forward 19 months and the deal - despite being two free transfers - is arguably the worst in the history of English football.
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Sanchez has now joined Inter Milan on loan, while Mkhitaryan is at AS Roma on a temporary basis.
Both players have been utterly hopeless in the last year-and-a-half, with Sanchez (five in 45 appearances) and Mkhitaryan (nine in 59 appearances) amassing just 14 goals in total.
And as revealed by the Daily Mail, the two players are on course to cost Arsenal and United nearly £50m in wages alone.
Sanchez's basic wage of £300,000-a-week has already cost the Red Devils £24.9m and this isn't taking into account the lucrative bonuses in his contract that they have had to pay.
The Chilean will also cost the club £6.5m in wages in 2019/20 at Inter, with United subsiding his salary despite the fact the deal has no 'obligation to buy' clause.
As for Mkhitaryan, his basic pay of £180,000-a-week cost Arsenal a cool £15.1m, but at least the Gunners have got him off the wage bill entirely this summer.
Roma will also pay between £3-£4m to take the Armenian on loan, a small silver lining.
But the figures certainly do not lie and the Sanchez/Mkhitaryan swap deal will forever be etched into fibre of Premier League folklore - for all the wrong reasons.News Now - Sport News