When Arsenal and Manchester United meet in the FA Cup this weekend, it will be almost seven years to the day since one of the most fateful and regrettable transfers in Premier League history. It was a move that had long-lasting consequences for both clubs, many of which are still being felt now, and the decision has forever tainted the reputation of the player involved.

At the moment of his arrival at Old Trafford, on January 22, 2018, Alexis Sánchez was widely considered one of the best players on the planet. By the time of his departure to Inter Milan, only 19 months later, he was regarded as both a spent force and the face of the toxicity that had gripped United.

The story of Sánchez’s calamitous spell in Manchester is well known. The player himself has provided much of the colour, saying in 2020 that he wanted to leave after just one day. “I remember the first training session I had, I realised a lot of things,” he said. “After the session I got home and I told my family and my agent, ‘Can you not rip up the contract to go back to Arsenal?’”

If such a revelation paints a picture of the Chilean’s emotional state at the time, then his numbers tell the story of his abject performance. In his final full season at Arsenal, Sánchez scored 30 goals in 51 matches. In his only full season at United, he scored just twice in 27 matches.

Now 36, Sánchez has successfully rebuilt his career after those painful days in Manchester. He is back at Udinese, the club where he first made his name in Europe, having won two Serie A titles with Inter Milan. In 2022-23, he was named Marseille’s player of the season.

Moving on from that deal in 2018 has proved easier for the player, then, than it has for United. All these years later, the club is still paying the price for the decision to give Sánchez a contract worth an eye-watering £560,000 a week.

Such was the size of Sánchez’s deal (which later cost £9 million to terminate), it effectively obliterated United’s wage structure. For players and their agents, it set a new ceiling for negotiations and inflated every salary tier. Players who earned in the region of £100,000 a week were now asking for £200,000. Players on £200,000 a week were now expecting £300,000.

Within around 18 months of Sánchez’s arrival, United had improved Marcus Rashford’s terms to around £250,000 a week and made David de Gea the highest-paid goalkeeper in the world, on around £375,000 a week. Even less important players, such as Victor Lindelof, were able to renegotiate deals with significantly improved terms.

Perhaps the most glaring example of the knock-on effect were the negotiations around a new deal for midfielder Ander Herrera, who demanded £350,000 a week to stay as his contract ran down. It would have meant United more than doubling his salary and he ended up leaving as a free agent for Paris St-Germain in July 2019.

Sánchez’s deal proved to be seriously destabilising for United, both on the balance sheet and in the dressing room. When one player earns so much more than everyone else, his team-mates expect results. Sánchez earned superstar money without ever delivering superstar performances.

That contract represented a grievous error by United, and they compounded it in subsequent years by failing to learn their lesson. If there was one overarching lesson from the Sánchez deal, it was that offering huge contracts to ageing players was a risky move – and yet United have repeatedly fallen into the same trap since 2018.

The likes of Edinson Cavani, Raphaël Varane, Cristiano Ronaldo and, most recently, Casemiro, have all joined United aged 28 or older, on enormous wages. None of them justified the expenditure, with United now scrambling to find a buyer for Casemiro to free up finances this month. A significant reason for United’s lack of financial flexibility is that their huge wage bill is weighing them down.

At the same time as Sánchez’s deal was ripping up United’s wage structure, Arsenal were dealing with a problem of their own. A few days after losing Sánchez, they handed Mesut Ozil a contract worth £350,000 a week. It proved to be similarly ill-fated.

Arsenal’s adapted approach

The difference between the two clubs, though, is that Arsenal have adapted – at some expense, it must be said – to the problem created by Ozil’s salary. Instead of allowing Ozil’s terms to gradually inflate the wages of the entire squad, Arsenal soon embarked on a series of savage contract terminations. They paid an array of senior, expensive players to leave and instead prioritised younger talents on lower base salaries.

Prior to this summer, when there was a conscious drive at Old Trafford to target youth, the average age of United’s signings since the summer of 2020 was around 27. In that same period, the average age of Arsenal’s signings was below 25.

Is this how Sánchez will be remembered? As some sort of harbinger of financial chaos? For United, that is probably the case. At Arsenal, it is a little different. Sánchez was not a particularly popular figure within the club – sources describe him as being more interested in his dogs than in making friends in north London – but he was loved by the fans for his maverick style of play.

Indeed, how the Arsenal fans would love another player of his type on the flank in their current team. A winger who could make things happen out of nowhere, scoring all types of goals and generating chances with his vision and dribbling.

Such talents are not easy to find, which is why most of England’s smartest clubs are now targeting young talent with the potential to grow. The big-money moves for players at their peak are often the riskiest deals of all, and it can take years to undo the damage done by one bad decision.