Manchester City won the Premier League in 2013-14. Chelsea were champions 12 months later. After seasons in which they amassed 86 and 87 points, respectively, they have relapsed this year. While City are Capital One Cup winners and Champions League semifinalists, they are on course for their lowest league points tally in seven years. Chelsea are set for their lowest haul in two decades. Yet disappointment has come in different fashions.
The start
City's start was deceptively good and suggested they may run away with the title. They won their first five games, all without conceding. They were top as recently as the middle of December, though the more telling fact was that their defeat at Arsenal before Christmas was already their fifth of the league campaign.
Yet while City began brilliantly, Chelsea, who tend to be early-season table-toppers, started atrociously. They were 11 points behind City after five games. They lost nine of the first 16, rendering it the worst title defence in Premier League history. While their first defeat was inflicted by City, a 3-0 at the Etihad Stadium in August, their problems began even before then: the opening-day draw with Swansea saw Thibaut Courtois sent off and Jose Mourinho criticise two members of the medical staff for coming on to the pitch to treat Eden Hazard. Doctor Eva Carneiro's legal case against the club has still not been resolved.
The signings
Another way in which City seemed better equipped. They spent £158 million, a record for an English club in a transfer window, and recruited Nicolas Otamendi, who manager Manuel Pellegrini had described as the best defender in La Liga last season, plus, in Raheem Sterling and Kevin De Bruyne, two of their three major targets. The third, Paul Pogba, eluded both them and Chelsea. So, too, did Everton's John Stones, another Mourinho target.
Chelsea ended up spending over £70 million without obviously strengthening the side. Pedro seemed a coup when they snatched him from under Manchester United's noses, but his displays have been mixed. Mourinho rarely trusted the £20 million left-back Baba Rahman. The deadline-day acquisitions Papy Djilobodji and Michael Hector have played one minute of first-team football between them. The fault lines at the club were apparent, unlike at City, where Pellegrini preserved the impression of harmony.
Yet if Mourinho was unhappy at many of the additions, he has to shoulder responsibility for the disastrous decision to bring in Radamel Falcao, scorer of a single goal. If Asmir Begovic, a fine understudy to Courtois, represents Chelsea's best buy, City's outstanding recruit, De Bruyne, ranks among the best players in the country. It all adds to the sense City should be doing better.
The strikers
Another contrast. Together with Tottenham's Harry Kane, Chelsea and City possessed the two best in England last season. While Sergio Aguero has retained his form, Diego Costa's campaign has been unhappy. The Spain international returned unfit, by his own admission, was criticised for his form by Mourinho and only scored three league goals by Christmas. A subsequent revival under Guus Hiddink came to a shuddering halt when his sending off and other antics at Everton in a FA Cup contest led to a three-match ban.
Aguero, meanwhile, has remained prolific, with City's issues the two spells he has spent on the sidelines and the absence of high-class alternatives. Wilfried Bony and the underused Kelechi Iheanacho have only seven league goals between them. Edin Dzeko and Alvaro Negredo, albeit in a different system, scored 25 in 2013-14, while the other Chelsea front men, in Falcao, Loic Remy, Bertrand Traore and Alexandre Pato, have only contributed five.
Defensive difficulties
The area in which Chelsea's decline was most visible. They clinched the title last year during a 16-game sequence when they only conceded nine goals. In the 16 league matches before Mourinho was sacked, they let in 18. Branislav Ivanovic's form vanished and John Terry, Gary Cahill and defensive midfielder Nemanja Matic lost their places at various points, while Courtois was injured.
City's defensive record can be split into two sections: with Vincent Kompany on the pitch, when they have only conceded six league goals; and without, despite the presence of Otamendi and Eliaquim Mangala, the two most expensive centre-backs in Premier League history. Their bad days have been particularly awful, letting in four apiece to Tottenham and Liverpool, and three in the rematch with Jurgen Klopp's team and also against Leicester.
Managerial upheaval
Chelsea fared worse before a change at the helm while City's difficulties increased after one was confirmed. The Londoners are unbeaten in the league since Mourinho's December departure, after nine defeats in 16 games and with the club 16th in the table. His interim successor, Hiddink, has said that avoiding relegation was his first task.
City announced on Feb. 1 that Pep Guardiola would replace Pellegrini. They promptly lost three of their next four league games. The sense that the Spaniard's arrival would galvanise the team seemed misplaced.
Home humblings
Stamford Bridge and the Etihad Stadium had become fortresses, the two hardest places for visitors to win. Not this season. Mourinho had only lost one of his first 99 home league games as Chelsea manager. His team were then beaten in four of six. City had only lost five home league games in four seasons. They have already equalled that tally this year. The certainties of old have been destroyed, along with something that underpinned title challenges.
Struggling stars
Something that was more prevalent at Stamford Bridge than at the Etihad. Until Mourinho's departure, only Willian had really performed to his potential. Even now, Costa's season is unsatisfactory, Matic and Oscar rarely start and Hazard, the reigning Footballer of the Year, is yet to score a league goal.
City's case is more mixed, as befits a mercurial team, and one with 13 points more. De Bruyne, Aguero, Kompany, Fernandinho and Joe Hart emerge in credit. David Silva, troubled by an ankle problem, has failed to reach the heights he touched in previous years. Yaya Toure represents an ageing enigma, Otamendi and Mangala players who have shown inconsistency but play in positions where consistency is a prerequisite.
Troubles against the top teams
Mourinho's side used to be defined by their ability to defeat their peers. While Chelsea have retained their age-old habit of overcoming Arsenal, they have only taken four points from a possible 21 against Leicester, Tottenham, West Ham and the Manchester clubs.
City's 3-0 win over Chelsea in August felt auspicious, but the champions' decline has rendered it less so. They are yet to beat members of the current top six, a statistic that explains why they languish 15 points behind Leicester. In England, although not in Europe, they have been flat-track bullies.
The injuries
City arguably have more cause for complaint. Kompany has only started 12 league games, Aguero has had two separate six-week absences and De Bruyne did not feature in February and March. Pellegrini felt they were without an average of six players per game in autumn.
Chelsea can cite Kurt Zouma's season-ending cruciate problem and the stop-start campaigns players such as Hazard and Terry have endured. They have more absentees now, albeit when they have less to play for. Yet the alternative argument is that a club with their resources ought to be able to cope.
The outcome
The fact that City are 13 points ahead of Chelsea is one illustration that their underachievement is less egregious. City's league season is still alive, with a top-four finish at stake, whereas Chelsea's has been over for weeks. City have had players who have at least performed for periods, even if form or fitness has prevented them from sustaining excellence.
Yet the reality is that a game which, when the fixture list was released, looked like a title decider is 10th against fourth. It will be a one-off: Hiddink and Pellegrini will not meet again at the helm of these clubs. Next season's clashes will pit Antonio Conte against Guardiola. Much, much more will be expected. The Premier League's underachievers will be charged with becoming achievers again.