As well as providing some momentary respite from the relentless Premier League season, this weekend’s FA Cup fixtures allowed breathing space to anticipate potentially the most competitive title battle in a decade.

With Chelsea stuttering their way through December and Man United continuing to miss the ruthless presence of Cristiano Ronaldo, neither appear capable of pulling away at the top of the table. Add a surprisingly resilient Arsenal to the equation and many believe a three-way tussle will take us right to the wire in May.

All of which is quite astonishing when you consider Chelsea’s form just over a month ago. In what appeared to be a season defining performance at the Emirates Stadium, it was difficult to argue with those already crowning the West London club worthy champions. Balancing brute force with cold-blooded efficiency, Carlo Ancelotti’s well oiled machine annihilated Arsenal with a showing that won’t be bettered this campaign.

But just as the Stamford Bridge faithful seemed ready to crown Ancelotti rightful heir to Mourinho, Chelsea hit December and a Scolari-esque train-wreck of form. Nine points from a possible eighteen is concern enough, but the level of performance was even more worrying. The impact of the African Cup of Nations has previously been played down, but a stuttering Chelsea without the phenomenal Drogba must concern Ancelotti. Ending January with their two point cushion intact will now represent a massive success.

To most managers, the sale of Ronaldo and Tévez would represent an undisputable crisis. But Sir Alex Ferguson is no mere mortal, and the challenge of retaining the title without these two talismanic figures will have been relished. To be within touching distance at the top, particularly in spite of the poor form of key players is a testimony to the resilience of the Man United manager.

Wayne Rooney’s best season in a Man United shirt and Darren Fletcher’s unlikely development into an accomplished central midfielder have been key to the challenge. And as Antonio Valencia grows in confidence each week, the record of four consecutive league titles looks more and more achievable.

Arsenal’s defeat to Chelsea at the end of November saw the preposterous anti-Wenger brigade sharpening their pencils once again, with the tired accusations of a lack of strength and experience levelled as reasons for a failure to compete. Since then, Arsenal have shown themselves to be a far better side than last season. Once again Wenger has used his limited financial resources brilliantly, replacing Kolo Touré with one of Europe’s most promising central defenders in Thomas Vermaelen.

The patchy form of the top two has undoubtedly helped Arsenal stay in touch, as has the emergence of Aston Villa, Tottenham and Man City. With fourth place no longer a given, they have worked hard to stifle the complacency that had previously been all too evident.

However, Arsenal will still fade in the final third of the season. Not because of their inexperience or lack of physical strength, but due to unfortunate injuries to their two best players. Robin van Persie’s season-long absence and Fàbregas recurring hamstring problems are the equivalent to Chelsea losing Lampard and Drogba. More than enough to scupper a sustained challenge.

With the transfer window already letting in a draught, rumours are rife that both Chelsea and Man United are ready to strengthen. Ancelotti and Ferguson will be acutely aware where their respective squads need reinforcements, but possibly more aware that the transfer window is synonymous with knee-jerk signings. If the red tops are to be believed, both clubs are eyeing battering ram centre-forwards, with Chelsea after Emile Heskey and United considering Porto’s Hulk.

With Michael Owen failing to live up to his ridiculously lofty billing, it is clear that United need a second world class striker. But Ferguson is far too wily to choose the raw Hulk over a summer move for the polished and proven David Villa. In the meantime, the United boss will hope to coax Dimitar Berbatov into the form that prompted his signing from Tottenham two years ago.

Chelsea will also do well to sidestep the short-term fix of Heskey. Daniel Sturridge’s first goals for the club will have been enough to convince Ancelotti that he can hold the fort until the return of Drogba.

However, the potential transfer ban facing Chelsea does pose some intriguing questions. Will they see January as their final opportunity to invest for two years? If so, they may move for Franck Ribéry. With Deco woefully inadequate at the tip of the diamond and Joe Cole struggling to recapture his best form, the Frenchman could be the key in unlocking those stubborn mid-table teams who seem intent on derailing Chelsea’s title challenge.

Regardless of the transfer window, this season’s champions will be the team with the most staying power. Where Man United’s hat-trick of titles was built on the cornerstone of Ronaldo’s individual brilliance, this campaign is all about the best team. The squad that bonds more significantly in the face of adversity will be crowned champions. Keep watching… it won’t be over until May.