Mauricio Pochettino threw it out there earlier this week, boldly putting Harry Kane's long-term Tottenham Hotspur future in question.

The Spurs manager admitted that the club had to play its part in ensuring that the striker had no need to cast envious glances elsewhere or even choose to leave for a new challenge.

Pochettino's honesty was admirable, and unusual, in the modern game, with the Argentinean admitting that, at some point in the near future, Spurs must start to deliver on and off the pitch and prove that their ambition matches that of their leading players.

But for all of Pochettino's candour, the reality of Kane's progression and elevation into the superstar bracket is not that he may soon become too big for Tottenham, but that he may also outgrow the Premier League.

It is not only Spurs who now face a fight to hold onto their prized asset. If Kane begins to grow restless with his failure to win a major trophy with his boyhood club, there is only a small number of teams who could prise him away from Tottenham and the odds are already stacked against another Premier League outfit striking a deal to take him away.

Tottenham chairman Daniel Levy only tends to do business on his terms and there will be no desire on his part to allow his club's biggest star to make a domestic rival stronger -- particularly at a time when Spurs are on the brink of moving into their new stadium.

But Levy will also have studied the transfer market closely over the past six months and realised that Neymar's world record €222 million move from Barcelona to Paris Saint-Germain was a serious game-changer.

Philippe Coutinho's €160m transfer from Liverpool to Barcelona at the weekend will have only served to reinforce the view that, if Tottenham were ever to consider selling Kane, the England forward would command a fee closer to that paid for Neymar than Coutinho.

Kane is the Premier League's most consistent goal scorer, he is now making his mark on the international stage and only three players -- Cristiano Ronaldo, Neymar and Roberto Firmino -- have scored more than his five goals in the Champions League this season.

Harry Kane played his part as Tottenham took four points off Real Madrid in the Champions League group stage. Ian Kingtonian/AFP

He is as close as you can get to guaranteed goals and, at 24, he has his best years ahead of him at a time when both Ronaldo and Lionel Messi are the wrong side of 30.

Manchester United, despite investing an initial £75m in Romelu Lukaku last summer, would love to take Kane to Old Trafford, but would they, or indeed could they, afford to spend close to the price paid for Neymar to clinch a deal with Spurs?

It is difficult to imagine United financing that deal and Kane would probably look at their ongoing transitional period and decide that better prospects lay elsewhere.

Manchester City, perhaps? Even City do not have a bottomless pit and, with the Premier League leaders unable to sell out for a Carabao Cup semifinal this week, the numbers game suggests that the money coming in through the turnstiles and off the pitch commercially would not stack up to make a move for Kane financially viable.

And also, with Sergio Aguero and Gabriel Jesus already in the squad and Alexis Sanchez seemingly on his way, would Pep Guardiola find a place for Kane?

Chelsea have reined in their spending in recent years, but Tottenham selling Kane to their bitter rivals is a non-starter anyway, so that would leave Barcelona, Real Madrid and PSG to fight it out for the Premier League's most impressive home-grown player.

Barca, having already used the Neymar fee to sign Coutinho and Ousmane Dembele, might struggle to raise the cash. But PSG have already displayed their readiness to break all records by signing Neymar and agreeing a €180m permanent fee with Monaco to turn Kylian Mbappe's loan into a permanent deal in the summer.

Mauricio Pochettino has insisted Tottenham would only let Harry Kane leave if he asked to go. Julian Finney/Getty Images

Real are the club who would appear to hold the all the aces in any pursuit of Kane, however. They need a long-term replacement for Ronaldo's goals, while Karim Benzema has only weighed in with two league goals this season, and their recent lack of big-spending is comparable to a smoking volcano waiting to erupt.

Having fallen behind domestically this season, there will be a determination within the Bernabeu to hit back and Kane ticks all the boxes. He scores goals, he is young enough to have a bright future, he is ambitious and, crucially, many of Real's rivals have obstacles to overcome in order to sign him.

Spurs may well be able to persuade Kane that he can achieve all of his ambitions with them, but even the man himself has spoken recently of the need for the club to win trophies now.

If the clock is ticking on his Spurs future, then it is also ticking on his time in the Premier League.

As much as it sells itself as the biggest and most exciting league in the world, the Premier League has still to find a way to keep its biggest stars from the clutches of La Liga's superpowers.

Whether it is David Beckham, Michael Owen, Thierry Henry, Ronaldo, Gareth Bale, Luis Suarez or Coutinho, the Premier League's superstars always end up in Spain and Kane will be the next one in La Liga's sights.