This summer, Chelsea are faced with a dilemma that the Premier League's five previous champions all failed to answer.

Indeed, retaining the Premier League title is a significantly tougher challenge than you might believe. Throughout the Premier League's 24-year history, only two managers and two clubs have lifted the crown in consecutive campaigns - Sir Alex Ferguson's Manchester United and Jose Mourinho's original Chelsea cast - and no side has done it since 2009.

The Premier League's golden rule is that you simply can't stand still. Whether you're fighting relegation or honing in on its biggest prize, the English top flight has a knack of chewing up and spitting out clubs who fail to improve their squads over the course of the summer transfer window.

Take Roberto Mancini, for example. He bemoaned the unspectacular additions to his title-winning Manchester City side made in summer 2012- Jack Rodwell, Javi Garcia and Scott Sinclair - and was sacked a year later after enduring a trophy-less campaign. Likewise, David Moyes could only rope Maroaune Fellaini into the silverware-laden United rabble he inherited from Ferguson, eventually followed by Juan Mata in January, and received his marching orders after just 10 months at Old Trafford.

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Spanning back even further, the underwhelming threesome of Manuel Almunia, Emmanuel Eboue and Mathieu Flamini arrived in north London after Arsenal's iconic 'Invincibles' 2003/04 season. The Gunners haven't touched the Premier League title since.

The old adage, to paraphrase Alan Hansen, is not to fix what isn't broken - an understandable, natural reaction that has manifested inside the mind of Jose Mourinho already this summer. Yet, recent history suggests it's a dangerously misguided fallacy, often ending in failed title defences and ultimately, managerial departures. So the question now facing Chelsea is whether they've improved enough this summer to become the Premier League's first title retainers in six years.

Their business thus far has been somewhat disenchanting, compared to Manchester United's recruitment of five players who featured at last summer's World Cup, Manchester City's record-breaking swoop for Raheem Sterling and Liverpool's subsequent £77.5million spend. Even the likes of Newcastle United, Swansea City, Stoke City and West Ham look set to defy the Premier League's balance of power next season following a window of progressive trade.

Rather than targeting improvements upon the starting Xi he rarely rotated last season - in itself, arguably a sign that Chelsea need more options - Mourinho has implemented a simple one-in-one-out policy, replacing club icons Petr Cech and Didier Drogba with Stoke Asmir Begovic and Monaco-come-Man-United's Radamel Falcao respectively.

Although both additions meet the impeccably high standards set at Stamford Bridge last season - Begovic boasting five campaigns as the Potters' No.1 but now serving as understudy to Thibaut Courtois and Falcao widely regarded as the best finisher in world football until enduring two injury-stricken seasons - neither drastically improve upon the talent in Mourinho's possession before, or create a new focal point of the starting line-up. The first team, the philosophy and the entire squad is practically identical.

Of course, history doesn't always repeat itself. The current Chelsea crop are much younger than the City squad who failed to defend the title twice and the clan of declining veterans Moyes inherited at United. In fact, with an average age of just 25.4 years they're actually the fourth-youngest side in the Premier League.

The confidence of claiming the 2015 PFA Player of the Year award will only further accelerate Eden Hazard towards the realms of Ballon d'Or; and that impact echoes throughout a young squad who took their first step towards dynastic dominance last season - a watershed moment in the careers of many. Likewise, as previously mentioned, Mourinho knows what it takes to lift the title twice in a row.

But overall, Chelsea were given a relatively easy ride last year. That might seem like an unnecessarily pessimistic view of a club that held top spot from the first match-day to the last and eventually finished just eight short of the Premier League's record points total - 95, set by the Blues in 2009/10. Yet they were never truly challenged by the other title competitors, who spent much of the campaign scrapping it out between themselves for avoidance of fourth spot.

It will be considerably different in the coming campaign; Arsenal are galvanised by their FA Cup-winning finish to last season, United have grown stronger with every transfer window under Louis van Gaal and Manuel Pellegrini's motivational stick comes in the form of the sacking axe, delicately lingering over his head. Simply repeating the form of last year might not be enough for a Blues side who struggled defensively in the first half of the season and offensively in the second - especially if they fall for City's eternal honey-trap of getting fat from their own success.

Does that mean Chelsea should be adding a superstar to their line-up this summer? If there's one available, yes. It may rock the boat, it may cause some teething pains. But it will also keep the title-winners of last season firmly on their toes, whilst sending out a statement of intent to the Blues' closest divisional rivals.

The likes of Borussia Dortmund's Marco Reus, Barcelona's Pedro, Atletico Madrid's Antoine Griezmann and of course, Juventus' Paul Pogba certainly come to mind. But whether the Premier League champions can facilitate a deal with just a month of the summer window remaining - and whether Mourinho holds the same concerns as me - remains to be seen.