This week, when they play Real Sociedad, Manchester United face their biggest game since 1990.

United have contested four Champions League finals, winning two and losing two, during that 35-year time frame, but none have been as consequential to the club's future as Thursday's Europa League round of 16 first-leg tie in Spain. The same will apply in next week's second leg at Old Trafford -- and every Europa League game until the final in Bilbao, Spain, on May 21 -- if United get that far.

The reason? Failure to win the Europa League would mean United miss out on a place in next season's Champions League, triggering a financial nightmare that would leave a 100 million hole (at least) in the club's budget at a time when money is already tight at Old Trafford.

United's Premier League struggles -- they sit in 14th position, 11 points behind sixth-place Newcastle -- and elimination from the FA Cup with a fifth-round defeat at home to Fulham on Sunday mean they cannot qualify for Europe via any other route this season than by winning the Europa League. Win it, as Jose Mourinho's United did in 2017, and the club will unlock the door to the Champions League's financial riches, fast-track United's path back to stability and enable coach Ruben Amorim to start the work of rebuilding the team.

But United are now playing a high-stakes game, and failure to win the Europa League will send the club sliding into a bleak future that could take years to escape.

The team are losing, the financial results are bad, staff at all levels have been informed of further job cuts to come -- adding to the roughly 200 who left in the final months of 2024 -- and supporters are planning a protest against the owners, the Glazer family, and Sir Jim Ratcliffe's Ineos Group before Sunday's clash at Old Trafford against Arsenal.

The Europa League offers United an escape route from their problems. Here's why it's vital they take it.

How bad are United's finances?

United have arguably not faced such a crucial fork in the road since Sir Alex Ferguson took his team to Nottingham Forest in an FA Cup third-round tie in 1990, knowing that defeat could cost him his job and change the course of United's history. In 2025, failure to win the Europa League this season will only exacerbate the club's perilous financial state, making it so much harder for them to return to the top.

Despite ranking fourth in the 2025 Deloitte Money League behind Real Madrid, Manchester City and Paris Saint-Germain in terms of revenue generated last year (United's revenue was 636.95m ($810m), United's costs saw them report a loss of 113m ($143.7m) during the most recent financial year.

The Premier League's Profit and Sustainability Rules (PSR) only allow for losses totalling 105m ($133.5m) over three years, but United have avoided infringing those limits so far because not all spending goes against calculations. Also, clubs can claim allowances known as "add-backs" including spending on infrastructure, youth development and women's football.

United's financial headroom due to PSR is now minimal. The most recent accounts covering the period between Oct.1-Dec. 31, 2024, revealed a 12% drop fall in revenue, operating profit down 88.7%, an increase in the club's debt to 515.7m ($655.4m) and a total of 414m ($526.1m) owed in transfer fees. [It's worth noting that owed fees aren't unusual in football: Chelsea (491m), Tottenham (307m) and Arsenal (268m) Manchester City (230m) and Liverpool (123m) also owe money on previous incoming transfers.]

Interest payments on United's debt are now 35m ($44.5m) a year and this season has also seen United pay out compensation totalling 14.5m ($18.4m) to manager Erik ten Hag, sporting Dan Ashworth and several coaches following dismissals earlier this season.

United's financial problems are why Ineos, which now controls the club as minority shareholders, have embarked on a huge cost-cutting drive including up to 400 job cuts, ticket price increases and the end of free meals for non-playing staff at the club.

More bad news: United earned 40.5m ($51.5m) from the Premier League merit payment scheme by finishing eighth -- their worst Premier League finish -- last season. With each position worth 3.1m ($3.9m), United would only earn 21.8m ($27.7m) if they fail to improve on their current position of 14th, leading to another significant drop in earnings.

Why is European qualification so important?

For clubs of United's stature, participation in European competition is crucial, and not just because of the money that can be earned from the UEFA pot known as the Distribution List.

Last season's Europa League winners Atalanta banked 18.23m ($23.18m) in prize money after beating Bayer Leverkusen in the final, and due to an increase in the money available following the 2024-2027 re-shaping of UEFA club competitions, the maximum figure a club can make from the Europa League Distribution List is now 27.04m ($34.41m).

United's quarterly accounts for the period Oct. 1-Dec. 31, 2024, show that the club earned 52m ($66.19m) from 10 Old Trafford fixtures during that timeframe; with the new extended League Stage of the Europa League guaranteeing every participant four home games, the club can add 20m ($25.46) and look forward to an extra 5m ($6.36m) with every European home fixture.

A winning campaign in the Europa League could therefore be worth at least 60m ($76.37) to United, but playing in the Champions League would take United's earning potential way beyond 100m ($127.32m) a season. UEFA's total Champions League prize pot for 2024-25 is 2.04 billion ($2.6bn) compared to the total 466.8m ($594.52m) on offer in the Europa League. Winning the latter would give United a place in the former, further easing the strain on their finances.

According to football finance blogger Swiss Ramble, six clubs -- Liverpool, Arsenal, Barcelona, Bayer Leverkusen, Inter Milan and Atletico Madrid -- earned in excess of 70m ($89.1m) from this season's League Stage alone. With incremental prize money at each stage between now and the Champions League final, this season's winners will earn 138m ($175.7m) from the competition.

Even the most optimistic United fan would accept it is unlikely that the team could win next season's Champions League, but even if they only play in the League Stage, they could get expect to earn a minimum of 50m ($63.6m) just from the prize pot alone, before accounting for gate receipts from four home games.

The financial gulf between being in the competition and out of it is clear: United's 90m-a-year ($114.6m) 10-year kit deal with adidas includes a 10m ($12.7m) deduction every season they don't play in the Champions League.

Missing out on the Europa League will cost United at least 40m, but the financial hit of not being in the Champions League starts at 100m and only goes up.

How do United compare to other clubs?

Last month, Liverpool posted their financial accounts for the year ending May 31, 2024, and the Premier League leaders reported a loss of 57m ($72.5m), with the club attributing a 38m ($48.3m) fall in media revenue to the team not participating in last season's Champions League.

Liverpool also highlighted a rise in costs to 600m ($763.6m), mainly salaries, which underscores the importance of European competition to clubs needing to service such high costs.

Arsenal, who returned to the Champions League last season for the first time since 2016-17, still reported a loss of 17.7m ($22.5m) for the year ending May 31, 2024. However, the financial benefit of being in the Champions League is highlighted by the fact that the Gunners reported a loss of 52.1m ($66.2m) the previous year.

Aston Villa reported a loss of 119.6m ($152.08) in their most recent accounts, but according to Deloitte, their wage bill to revenue ratio of 96% is the highest in Europe and another pointer to the importance of Champions League participation for Villa.

But to show that success on the pitch is the ultimate driver of financial well-being off it, Manchester City reported record revenues of 715m ($909.1m) and a profit of 73.8m ($93.8m) in their year-end accounts after winning a fourth successive Premier League title and 13 consecutive seasons of Champions League participation.

Why can't United just dump lots of players to raise funds this summer?

When a footballer signs a contract, the club have to honour it. If the player fails to perform, the club must find somebody else to sign them and hope that they are willing to pay an acceptable fee and take on their wages.

"Players sign fixed-term contracts for a set amount of time," Tom Keane, Head of Sport at the law firm Brandsmiths, told ESPN. "By contrast, most employees in this country have employment contracts that last for an indefinite amount of time but include a notice period allowing either side to terminate, for example on three months' notice. Such notice periods do not exist in player contracts. Unless that player does something that amounts to gross misconduct, the club cannot just get rid of them.

"As such, the only ways for the club to [move forward] are to either agree a mutual termination of the contract with the player, which is unlikely if the player is earning well under that contract and has no other club to join, or, more likely, to agree to transfer the player to another club who are willing to match the salary ... Without [the player, current club, and interested club] aligned, nothing can happen."

United's problem is that they have lots of players -- namely Marcus Rashford, Casemiro, Mason Mount and Antony -- who are surplus to requirements, but their diminishing transfer value (due to years of poor performances) and/or high salary makes it difficult to move them on without incurring a big financial loss.

United might have to subsidise a move for former academy star Rashford, now on loan at Aston Villa, due to a lack of clubs being prepared to take on the remaining three years of his 325,000-a-week salary.

Casemiro, a 70m ($89.1m) signing on a four-year contract from Real Madrid in August 2022, would be worth 17.5m ($22.2m) on the club's balance sheet next season due to the amortization of his transfer fee. As a consequence, United would need a club to pay 17.5m to sign the 33-year-old this summer -- anything less would be recorded as a financial loss, edging United closer to breaching PSR.

United need to rebuild their squad, but with money raised from moving on homegrown players -- who did not cost a transfer fee -- enabling any fee to be classed as pure profit in the accounts, players such as Kobbie Mainoo, Alejandro Garnacho and Rashford are the most attractive potential outgoings to the club. Any cash generated would be crucial to avoiding a PSR breach.

As for expensive flops including Casemiro, Mount, Antony, Rasmus Højlund and Joshua Zirkzee, United face little or no chance of avoiding big losses if they offload any of them. They are the football equivalent of extravagant credit card purchases with a big price tag and minimal resale value.

Is there a shortcut out of the mess?

Winning the Europa League is the quickest way for United to get back to somewhere close to a sound financial footing. It's a magic wand that opens the door to a brighter future, albeit one that would still involve servicing the debt and rebuilding the squad.

However, United's financial problems are deep-rooted and cannot be solved by annually walking a tightrope of attempting to qualify for the Champions League. United must either renovate Old Trafford or build a new stadium, which would cost at least 1 billion ($1.27bn). A squad overhaul is also crucial, but unavoidably expensive.

"If you look at United's most recent accounts, the fundamentals are still quite impressive from a match-day and commercial revenue perspective," Chris Mann, Head of Sporting Strategy at Sportsology, told ESPN. "But the poor performance on the pitch is really hurting them. It feels like they are stuck in a catch-22 situation -- a club with a Champions League cost-base and a mid-table reality, but at the same time as trying to make the team more competitive and get it back in the top six."

So is there a way out beyond simply winning the Europa League?

"Player recruitment is an area United need to improve," Mann said. "They have signed lots of players who haven't performed for significant sums and have therefore declined in value.

"There is also the route of private equity investment, something Ratcliffe has shown he hasn't been averse to securing with other businesses, and the City Football Group and Atletico Madrid have both taken this option in recent years, but the risk with that is investors wanting a quick return.

"The panacea would be the Glazers selling up completely and clearing the debt, but that is almost certainly not going to happen. Unfortunately, United are in a really difficult position and there are no easy solutions."

Ultimately, United need to win on the pitch to make everything better off it. And nothing could possibly be bigger right now than Amorim's team winning the Europa League this season.