With eight goals in seven games this season, after scoring in Sunday’s 3-3 draw with West Ham, it’s little wonder Spurs are reportedly looking to secure the future of the 28-year-old with a new deal.

Signed with modest fanfare for £22m from Bayer Leverkusen in 2015, partly with the view of helping to lighten the goal burden on Harry Kane, Son has progressed from a good player to one of the Premier League’s best.

But it’s only when the numbers are laid bare that the South Korean’s importance to Jose Mourinho’s side becomes wholly apparent.

And with his rise in performance comes the ever-increasing bonus of exposure in the Asian market, with research showing there are more Tottenham fans in Son’s home nation than there are in the UK.

Here is why Son is crucial to Spurs – who start their Europa League campaign on Thursday – on the pitch and off it.

For team – goals, and wins

Son, alongside Kane, has become the go-to man for Spurs.

His productivity when it comes to goal contributions has grown steadily in each of the five seasons he has completed for Tottenham.

In his debut campaign, he either scored or assisted 15% of all Tottenham’s goals, while last season that had risen to a remarkable 33% – scoring 18 and assisting 11 – even surpassing Kane’s contribution of 30%.

So far this term, he’s contributed eight goals and four assists, having a hand in 43% of Spurs’ 28 goals (Kane is on a remarkable 65%), and in his overall Tottenham career, he has been involved in just over a quarter of the club’s 543 goals.

Investment company Carteret Analytics, who provide some Premier League clubs with insight on potential signings, have charted Son’s increasing influence for Spurs.

Son’s Carteret Rating, a measure of his contribution towards winning games, grew from 243.1 in 2017-18 to 307.2 in 2019-20 – with Kane the only Spurs player to score higher last season.

For comparison, Lionel Messi’s rating last season was 418.2 and, if there was any doubt about how impressive Son’s start to this campaign has been, he’s currently on a rating of 526.7 – although that would be expected to level out with only five Premier League games of data to analyze so far.

For himself – 25th best player in the world

Son arrived as a relative unknown to English football fans, when he made the move from Bayer Leverkusen five years ago.

The Global Player Index, a ranking of players from Nielsen’s Gracenote and Hypercube based on what happens when they are on the pitch, rated Son as the 137th best player in the world when he landed in north London.

In May 2017 he became a fixture of the top 100 and this week, after his performance against West Ham, he peaked as the 25th best player in the world, according to the rankings.

It’s an improvement that can be measured by his proficiency in front of goal.

Gracenote’s metrics say, Son, given the chances he has been presented within the front of goal, has scored more goals than expected in every season since he joined Spurs.

In that time Gracenote says he has overperformed with goalscoring by 37% (60 scored, 43.66 expected) – only Eden Hazard has performed better across Europe’s top five leagues in the last five years (48 scored, 32.69 expected).

But his start to this season has been something special, scoring seven times from chances worthy of 2.99 goals – an over the performance of 134%.

Son’s Carteret Intrinsic Value, which measures how much a player is worth to their club based on performances, has risen from £38.2m in 2017-18 to £75.1m, just £3.4m lower than Kane.

For country – the Spurs boom in South Korea

Put all this together and a player who was already a star in his home country when he joined Spurs becomes an icon among his compatriots.

A recent survey by Nielsen Fan Insights found that more than 21% of South Koreans considered Tottenham their favorite overseas football team – that equates to 11 million people aged between 16 and 69, and more Spurs fans there are in the UK.

Manchester United are the second most popular overseas team in the country, supported by 6.1%, having been pushed into second place by Spurs in 2018.

All this extra commercial potential has been driven by Son, with interest in Spurs barely registering in South Korea before his arrival and the club’s popularity nowhere near as strong in any other Asian nation.

It all stacks up nicely for Tottenham, with Son providing results on the pitch and expanded markets off it, and will no doubt increase the north London club’s desire to keep him beyond his current contract in 2023.