Manchester City are aiming to become the first side to retain the Premier League title since Manchester United in 2009 this season, but what makes it such a difficult task?
The title has only been retained on seven occasions in the Premier League's 26-year history - six times by Manchester United and once by Chelsea.
Will Pep Guardiola buck the trend of the last decade and succeed where his Manchester City predecessors Manuel Pellegrini and Roberto Mancini failed? Here, we take a look at some of the obstacles he faces.
Maintaining motivation?
Jose Mourinho is the only manager other than Sir Alex Ferguson to have retained the Premier League title, but having failed to repeat the feat since 2006, he also knows just how difficult it is. In September 2015, when Chelsea's title defence was already unravelling in his second spell in charge, he insisted it was a question of mentality.
"There are two sorts of champions," he said. "There are champions who win something - and there are lots of them - but there are the other champions who win two, three, four, five, 10 or more titles. In this club, we have 25 champions from last year, but serial champions in this squad, how many?
"[John] Terry, [John Obi] Mikel, [Branislav] Ivanovic are serial champions. Almost every season they have something in the pocket. But how many more do we have? That's the point. Of course it's very difficult to win every season, especially in the Premier League, but you can be a serial champion in your approach and attitude. One thing is to be champion once, another is this mentality."
It remains to be seen whether Guardiola can turn Manchester City into serial champions, but it is only natural for motivation levels to drop after an achievement like last season's record-breaking title success. Will City's players stay hungry? Guardiola will take encouragement from Vincent Kompany's response to clinching the title in April.
"My team-mates might roll their eyes when I say this: I want to see how the reaction is going to be now," he said. "I've never been able to retain the title and want to see if this team has got it to carry on and be even more successful."
City can also learn from Ferguson, whose attitude to winning silverware at Manchester United was fundamental to sustaining their success.
"Winning a trophy doesn't really mean anything to me after it has gone," he said. "At the time, it is the most cherished thing. As soon as it's over, it's forgotten. Not forgotten, but it evaporates. Your next step is the important one, and the mentality here is of that nature. The players are brought up to go for the next thing."
Ferguson nurtured that mentality over the course of more than two decades at United. Guardiola needs to achieve the same in a much shorter timeframe at City.
Opposition upping their game
While Premier League title winners sometimes struggle to maintain motivation, their opponents become more determined than ever to beat them. The champions are a prized scalp. Their direct rivals become desperate to bring them down a peg and lesser sides are always fired up to cause an upset.
By the time it comes to defending the title, opponents are generally more clued up about what to expect, too. They have had a full season to figure out the champions' blueprint for success, meaning they often have a better idea of how to frustrate them and exploit their weaknesses.
This was true for both Leicester in 2015/16 and Chelsea in 2016/17. Leicester's major weapon in their title-winning campaign was their speed and directness on the counter-attack, but teams soon wised up to their approach, sitting deep, guarding against the break and preventing Jamie Vardy from running in behind.
Chelsea, meanwhile, outfoxed their opponents using a 3-5-2 formation, but by the start of Antonio Conte's second season in charge, the rest of the division had begun to adopt the same approach. Chelsea's opponents learnt how to match up to them. The element of surprise was gone and they no longer held the same advantage.
City must prepare themselves for better-prepared opponents, too.
Transfer market dilemma
One of the biggest dilemmas facing a title-winning side is how to approach the subsequent transfer window. The challenge is to find the right balance between strengthening the squad and maintaining the harmony in the dressing room, but there is no exact science to it.
In 2000/01, Manchester United retained the title without making a single signing, but a year later they finished third despite a spending spree which saw Juan Sebastian Veron, Diego Forlan and Ruud van Nistelrooy arrive at Old Trafford. The recruitment drive was intended to consolidate their position at the top but instead it knocked them off their stride.
Sticking with what worked so well in the previous season is not always the answer, however. In fact, there are plenty of examples to suggest the opposite. After Arsenal's unbeaten 2003/04 season, Arsene Wenger's only signings were goalkeeper Manuel Almunia and youngsters Robin van Persie, Mathieu Flamini and Emmanuel Eboue. They went on to finish 12 points behind Chelsea in the following season.
The right signings can reinvigorate a title-winning squad and ensure the previous year's champions do not take their starting spots for granted. After Manchester United's 2006/07 success, for example, the arrivals of Carlos Tevez, Owen Hargreaves, Nani and Anderson improved the team and paved the way for an extended period of dominance.
That's what Manchester City are aiming for now. Many have questioned the arrival of Riyad Mahrez, wondering how he will hold down a starting spot in Guardiola's starting line-up, but he is a high-calibre signing with title-winning experience, and importantly, his presence in the squad should also keep Raheem Sterling and Leroy Sane on their toes.
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