In the summer of 2014, Chelsea were widely praised for enjoying a brilliant transfer window, when then-manager Jose Mourinho and the hierarchy of technical director Michael Emenalo and director Marina Granovskaia moved quickly to vastly improve the squad.
A season earlier, Mourinho's first back in England, the Blues had lacked goals and creativity - Eden Hazard was the only player to score in double figures in the Premier League in 2013-14 as Chelsea finished third, 30 goals behind champions Manchester City and Liverpool.
The work to mount a serious title challenge in 2014-15 had started six months earlier in January, when Nemanja Matic arrived from Benfica.
However, goals remained the top priority that summer, so in came Cesc Fabregas quickly in mid-June, while Diego Costa and Didier Drogba came a month later, while Loic Remy arrived on deadline day.
Chelsea player ratings vs PSG
Chelsea player ratings vs PSG
1/11 Courtois 5 out of 10
Overall, the goalkeeper had an OK game and did well in one instance to put off Ibrahimovic from taking a shot at goal. However, he endured some nervy moments, which will lead to questions of his form this term.
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2/11 Azpilicueta 3 out of 10
Will feel disappointed to have first allowed Rabiot to get past him and tap in the opener before completely losing Di Maria in the build-up to Ibrahimovic's goal. A game to forget for the Spaniard.
3/11 Cahill 5 out of 10
Was dragged out of position to deal with the pace and threat of PSG's forwards in a few instances, but worked well alongside Ivanovic
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4/11 Ivanovic 6 out of 10
Was caught out of position for Rabiot's goal, but made a last-gasp clearance to deny Di Maria in the fifth minute before making several other key blocks later in the game.
5/11 Kenedy 4 out of 10
Left Ibrahimovic with too much space and time to send in his cross to Rabiot, who subsequently scored. He did well going forwards but struggled defensively in an unfamiliar position.
6/11 Mikel 5 out of 10
Made some key tackles when needed to stop some of PSG's attacks - one of which resulted in a yellow card - while linking up well with his teammates. But could have done more to stop the ball that found its way to Di Maria in the build-up to PSG's winner.
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7/11 Fabregas 5 out of 10
Booked for a first-half foul on Motta, the Spaniard had a few good moments in attack but could not dictate the pace of the game.
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8/11 Pedro 6 out of 10
Superbly helped create Costa's goal after linking up with Willian while he impressed several times going forward but also worked hard to track back and defend too.
9/11 Willian 7 out of 10
Began the move that led to Costa's goal after winning the ball off Motta, and was generally impressive. He remains Chelsea's stand-out performer of the season even if he couldn't get on the scoresheet due to Trapp's heroics in goal.
10/11 Hazard 5 out of 10
Started the game off well - testing Trapp on a few occasions, but ultimately failed to dominate Chelsea's attacking play. Was booed off by a section of the home fans in the second half.
11/11 Costa 8 out of 10
With Chelsea trailing 1-0, the striker remained calm and composed to level the score with a fine effort in the 26th minute. Was a constant menace for PSG's defence and could have gotten more goals but saw his game cut short through injury.
With the ageing Ashley Cole no longer up to the task and not offered a new contract a new left-back, Filipe Luis, was also identified and signed quickly so that Cesar Azpilicueta could move back to the righ.
Financial Fair Play still mattered back then so players had to be sold to cover the £85million expenditure. No problem there, as the sales of David Luiz (£50m), Romelu Lukaku (£28m), Demba Ba (£5m) and a couple of others meant Chelsea's net spend was negligible.
August 2014, 19 months and three transfer windows ago, is the last time that Emenalo and Granovskaia can be proud of their work.
Since then the Chelsea squad, so dominant last season on the way to winning a first Premier League title in five years, has continually been eroded and reduced to the shell that was seen chasing shadows against Paris Saint-Germain in the Champions League on Wednesday night.
Just look at the difference in the Chelsea and PSG teams on Wednesday.
Kenedy, a 20-year-old winger with only 50 professional games under his belt, starting at left-back because Chelsea have no defensive depth. Yes Chelsea had two key players (John Terry and Kurt Zouma) injured, but having only five first-team ready defenders to cover four positions over a season is a recipe for disaster.
Their first-choice left-back (Cesar Azpilicueta) is really a right back; their first-choice right back (Branislav Ivanovic) is better in the centre; their fourth-choice centre-back (Gary Cahill) had his flaws brutally exposed by Zlatan Ibrahimovic.
Beyond those players Chelsea don't have any senior defenders to call on. 21-year-old Baba Rahman, bought for £14m and potentially rising to £22m, can't defend and looks completely out of his depth. Matt Miazga, 20, is not yet ready for the rigours of European football, interim manager Guus Hiddink has previously admitted. Talented academy prospects Nathan Ake and Andreas Christensen are out on loan and currently of no use to Chelsea. Jake Clarke-Salter, an 18-year-old academy graduate, is one or two injuries away from playing.
How did that happen? Mourinho must take a big portion of the blame. He never really gave Filipe Luis a fair crack and he became unsettled when Azpilicueta continued on the left; he sold Ryan Bertand, one of the Premier League's best left-backs this season, way too early; Ashley Cole still had a little bit to offer, even just as an experienced old head. Chelsea would have been better with any of those three at left-back than Kenedy - the first PSG goal on Wednesday came with the Brazilian 20 yards ahead of the danger.
The defenders they did bring in this summer? Rahman, Papy Djilobodji, so unwanted he was loaned out after playing just a minute of football against Walsall, and Michael Hector, loaned immediately back to Reading and anchoring the defence of a team 14th in the Championship. Miazga, arrived in January and still hasn't made his debut.
Further forward the problems are just the same and the options just as week. Good players were allowed to leave during Mourinho's tenure, and again, he must take some blame for that. Juan Mata, Andre Schurrle and Mo Salah are have proved that free from the Portuguese's tactical constraints they have more than enough ability to flourish.
Perhaps that was why a portion of control over transfers was taken out of Mourinho's hands in the summer. However, Mourinho had a clear vision of how he wanted his team to play, and that trio didn't fit it. Taking control out of his hands and putting it in the hands of Emenalo and Granovskaia having has only seen Chelsea's transfer policy become so much worse.
Emenalo and Granovskaia's failure to identify first-team ready targets in the last 18 months has hurt. Chelsea and Mourinho were linked with top quality defenders (Raphael Varane, Alex Telles, Aaron Creswell, Gregory van der Wiel) all summer and ended up with Rahman, a player the Portuguese clearly never wanted and who is clearly not going to be ready for regular football for a while.
Mourinho never wanted to sell Petr Cech, a move made out of sentimentality that obviously backfired - Cech joining Arsenal mightily improved Chelsea's closest rivals in their weakest area.
The Portuguese also made it clear that he wanted more attacking options, Juan Cuadrado didn't work out (wasn't given the chance by Mourinho), Diego Costa was injury prone and Loic Remy had made it obvious he wanted to leave to play more. Radamel Falcao was a huge error and although Pedro eventually arrived, by then the first nail had already appeared in an aggravated Mourinho's coffin after the Dr Eva Carneiro affair.
With Mourinho gone January came around and Chelsea again failed to strengthen - in fact, the squad was further weakened. Ramires fetched a big fee but he had been an extremely useful player for years. The uninterested Remy wasn't sold. In came Miazga and the lesser spotted Alexandre Pato - so far a completely puzzling waste of space.
The lack of options was brutally exposed when Diego Costa came off injured at Stamford Bridge on Wednesday. Chelsea were in the game up until that point but Costa was replaced by another 20-year-old in Bertrand Traore; the Burkinabe may be talented, but he's not going to strike fear into the opposition just yet.
Chelsea's opposition may not quite follow the same financial restrictions but the difference in quality and options was a huge step. Loss of form amongst some of Chelsea's players - Eden Hazard and Nemanja Matic chief among them - cannot be ignored, but one can easily make the case that Chelsea players wouldn't be so stale, fatigued and disinterested if there was more competition for places in the squad. The top players have known for a long time that they are starting every game, no matter how poorly they play.
When PSG's most influential midfielder, Marco Verratti, was ruled out, they could turn to Adrien Rabiot - a player valued at £30m and linked with Arsenal and Manchester United in recent months.
From the bench came Netherlands regular Gregory van der Wiel and Edinson Cavani and Javier Pastore, a pair of attackers bought for more than €100million.
Once upon a time, Chelsea had a squad that boasted two top class players in every position. That is obviously no longer possible, because of FFP and the need to turn a profit, but the Blues no longer boast one top class player for every position.
The squad needed improving in January 2015 when it was clear that Chelsea's stars were slowing down due to a lack of competition and playing too much. It didn't happen and Chelsea were dumped out of the Champions League in embarrassing fashion by PSG, although they ground out enough results to win the Premier League.
The squad needed improving in summer 2015 to maintain another title charge by adding new faces to lift a stale group. It didn't happen and was the first step to setting Mourinho down a path that would eventually see him sacked and put Chelsea in danger of relegation.
The squad needed improving in January 2016 with Chelsea fans still believing they may just sneak back into Champions League contention and/or win a trophy under Guus Hiddink. It didn't happen and now the Blues are out of Europe's top competition, unlikely to qualify next season and have only the FA Cup to look forward to.
It's been a gradual watering down of a once strong squad and the blame must lay firmly at the door of the Chelsea board.