With six points and a game in hand on their closest rivals, as just nine Premier League matchdays remain, you'd have to be loopier than Lord Looperson of Loopyville to bet against Chelsea walking away with this season's English crown.

Indeed, the Blues haven't surrendered pole position once since opening their campaign with a 3-1 win over Burnley, following the script set out by pundits and the press perfectly - barring unexpected slip-ups against Newcastle and Tottenham.

But where do Chelsea go from here? What's the next step in Jose Mourinho's master plan? Do the Blues simply hold onto the squad they've got, or does their roster need improving for the ever-difficult second album? With summer slowly approaching, it's time to consider the options.

That may seem a rather audacious suggestion. After all, Chelsea have spent £118million on new players this season, £27million of which was devoted to bringing Juan Cuadrado to Stamford Bridge just a matter of months ago. It's doubtful Roman Abramovich will deem further market exploits worthy after Chelsea's first Premier League title since 2010 and more spending, even when counteracted by the club's profit-spinning farming operation that's generated huge profits from the sales of Romelu Lukaku and Kevin de Bruyne to name a few, could see them fall afoul of Financial Fair Play regulations.

But there's no task tougher in English football than retaining the Premier League title. Manchester City have spent billions on their first team since the original influx of Sheik fortunes and they've now failed at their second attempt. Arsenal never managed it despite claiming the accolade thrice in seven years. Thus far, Sir Alex Ferguson and Jose Mourinho are the only managers to successfully defend the English crown and no club has done it since the Red Devils in 2008 and 2009.

More imperative than the quality of player is the mentality. Having failed to retain the title under two different managers, it's clear City's squad just doesn't have the appetite for it. Many view Chelsea as considerably more determined in spirit, but a marquee signing this summer will be crucial to keeping the Blues' current cast on their toes. Even the best get a little sloppy from time to time.

Furthermore, despite the considerable ease in which Chelsea have dominated the Premier League's summit over the last eight months, there are a few weak links throughout the squad - the first and most obvious being Gary Cahill.

In prior seasons, he's been Chelsea's most reliable defender, but this year the England international has made mistakes on some crucial occasions; destroyed by Harry Kane at White Hart Lane, passive as Bradford staged a 4-2 comeback in the FA Cup, flat footed as Edinson Cavani headed home for PSG at Parc de Princes. Kurt Zouma appears capable of filling Cahill's potential void, but with John Terry only edging closer to retirement, some new blood at the heart of defence - particularly offering a much-needed injection of pace - certainly wouldn't go amiss.

Real Madrid's Raphael Varane immediately springs to mind, but Mats Hummels or Neven Subotic of Borussia Dortmund, Valencia's Nicolas Otamendi, Everton's John Stones and Athletic Bilbao prodigy Aymeric Laporte represent somewhat more realistic options.

Another area the west Londoners could add to is central midfield. Although few dispute the quality and equilibrium of Nemanja Matic and Cesc Fabregas as an engine room partnership, retaining possession in the middle of the park for lengthy periods is one of the only weapons missing from Chelsea's arsenal. Another deep-lying playmaker within the squad, somewhat more superior and inventive on the ball than Ramires and John Obi Mikel, would vastly improve Mourinho's scope for tactical manoeuvre.

Perhaps Borussia Monchengladbach starlet Granit Xhaka, who has averaged an impressive 78 passes per match this season? A long-term investment that could pay off dividends. £8million-rated Manchester United target Lucas Biglia, PSG's disillusioned playmaker Yohan Cabaye and Monaco's Joao Moutinho remain alternatives.

This may seem like nit-picking; messing with a formula that's far from broken, despite Chelsea slowing down somewhat in recent weeks. But the Blues have had it easy this season; they've not beaten Manchester City or Manchester United, dropped points against Burnley, Sunderland, Newcastle and Southampton, and are still on course to stroll over the finish line.

With Liverpool showing vast improvements, Manchester United likely to come into their own next season, Manchester City out for revenge and Arsenal expected to finally address their dearth in defensive midfield this summer, it's imperative the Blues don't get left behind.