Chelsea's expansive Cobham academy has unearthed its fair share of talent over the years, but with such a steady flow of budding potential, several gems have slipped through before the club could tie them down to professional deals.

And none more regrettable than West Ham United phenom Declan Rice, who has forged his way into eminent standing on the Premier League scene and been instrumental in the Irons' ascension to European endeavours over the past few seasons.

Why did Declan Rice leave Chelsea?

Rice had spent much of his formative years earning his stripes among the academy ranks in west London, but, according to The Athletic, was released at just 14-years-old after concerns that his lack of physicality and vacillation from the coaches on where the young starlet's best position would be; indecisiveness and a heavy influx off players, resulting in his bitter termination.

Following a youth stint with Fulham, Rice found a home with West Ham where he earned his professional breakthrough and remains to this day.

Now 24 years old, the 39-cap England international has made 225 appearances for his east London outfit and scored 12 goals and assists apiece, and given the Hammers' qualification for Europe in both of the past two seasons, the club's rise to eminence coinciding with the emergence of the “monster” – as dubbed by ESPN’s David Cartlidge - comes as little surprise.

How much is Rice worth now?

How Chelsea must rue their decision.

Earlier this season, the £60k-per-week machine sent shockwaves through David Moyes' team by confirming to the club that he wishes to depart at the end of the season, hoping to taste coveted Champions League football for the very first time, and given his pedigree, his hopes of reaching the very top are probably justified, given the years he has devoted to ensuring West Ham return to the upper end of the Premier League.

Many of England's top outfits have expressed an interest, and among those Chelsea, who have reportedly been mulling over a move to complete their midfield with a superlative and iron-clad anchor, with his outfit demanding £100m to grudgingly grant his departure, although a fee of £70m now appears a more realistic proposition.

Hailed a "force of nature" by journalist Rob Blanchette, Rice could be the perfect cog to get the Stamford Bridge outfit whirring, with the Blues currently languishing in tenth place in the English top-flight and beset with a startling fall from grace.

As per FBref, the 6 foot 1 ace ranks among the top 7% of midfielders in Europe's top five leagues for pass completion, 11% for progressive passes, 11% for progressive carries and 5% for interceptions per 90, illustrating his refined scope and assurance as one of Europe's foremost industrious central engines.

Given Blues owner Todd Boehly has spent more than £550m on new signings since taking a seat at the head of Stamford Bridge's table last year, it would not come as a surprise to anyone if a formal offer were to be lodged.

But considering transfer funds needn't have been a discussion in the first place, had he just been granted time to continue his development and channel his ability into what it is at present, there will be an unequivocal and unanimous acceptance that the club had a nightmare on this particular prodigy.