Wu Lei has scored once in La Liga this season, in seven appearances

Midway through the second half, with his team nervously holding a 2-1 lead in a crucial relegation battle against visiting Real Valladolid earlier this month, Espanyol midfielder Sergi Darder received possession 30 yards from goal.

Darder held off a challenge and released a perceptive through ball, splitting open the visiting defence and sending his team-mate through on goal.

The striker, who had timed his run to perfection, received Darder's pass in his stride, took another touch to set up a shot and calmly stroked a confident low finish past onrushing keeper Jordi Masip and inside the left post.

On the other side of the world, millions of people leaped out of their sofas to acclaim a moment of history.

The goalscorer was Wu Lei, a national hero for football fans in China. And he had just become the first Chinese player to score in La Liga, in a game watched by an estimated live television audience of 25 million in his homeland.

With that huge level of support following his every move, the impact of the forward's arrival in Spain extends far beyond Espanyol's attempts to stay in the top flight. Because Wu is also at the heart of La Liga's bold attempts to unseat the Premier League as the most popular football league in the world.

As Espanyol prepare for a local derby trip to Barcelona on Saturday afternoon, BBC Sport finds out more.

More than a marketing gimmick

Fans hold aloft Wu Lei shirts at the game between Espanyol and Sevilla in March

Wu is the all-time top scorer in the Chinese Super League, netting 151 goals in 296 games for Shanghai SIPG and also becoming the focal point of the Chinese national team's attack, scoring 15 goals in 63 international appearances.

Despite that pedigree, there was still a great deal of scepticism in Spain when he was signed by Espanyol in January, with cynics suspecting the move was nothing more than a cheap publicity stunt orchestrated by the Barcelona-based club's Chinese president, Chen Yansheng.

It did not take long for the 27-year-old to win over the doubters. He immediately provided a much-needed spark to an Espanyol side which was in serious danger of the drop after a terrible run of form, having lost nine games out of 10 either side of the Christmas break.

His debut, away to Villarreal at the beginning of February, saw Espanyol stop the rot by earning a 2-2 draw. Then came a home victory over Rayo Vallecano, followed by consecutive draws against Valencia and Huesca, and - with the new arrival now deservedly established as a starter on the left wing - that historic moment of his first goal in La Liga in the 3-1 win over Valladolid.

Five league games, nine points, no defeats... Wu had joined a team which was in freefall and promptly played a significant part in their upturn in form. Not bad for a player who had been rudely dismissed as a marketing gimmick.

His new team-mates have been impressed, as long-serving midfielder Victor Sanchez told BBC Sport: "We didn't know much about him when he arrived and the truth is that he has surprised us. He's very quick, he can find space inside the box and he has an eye for goal.

"He has to improve tactically and with his associative play, but he has a lot of qualities. He is intelligent and has the capability to grow as he adjusts to our league. I think he will be a very important player for us."

Wu Lei's career stats to date Season Club League games League goals 2018-19 Espanyol 7 1 2018 Shanghai SIPG 29 27 2017 Shanghai SIPG 28 20 2016 Shanghai SIPG 30 14 2015 Shanghai SIPG 30 14 2014 Shanghai SIPG 28 12 2013 Shanghai SIPG 27 15

Challenging the Premier League

Aside from boosting Espanyol's attempts to stay in the top flight, from a wider perspective Wu is even more significant for the part he is playing in La Liga's determined efforts to catch up with - and eventually overtake - the Premier League in terms of worldwide popularity.

Traditionalists might not like it, but a basic truth of modern elite sport is that overseas markets are vital sources of revenue: from broadcasting, sponsorship and marketing deals.

For the last couple of decades, the Premier League has been totally dominant in that global landscape, raking in riches far exceeding anything commanded by other leagues: England's top flight currently earns around £5bn a year, compared to roughly £3.5bn for Germany's Bundesliga and £3bn for La Liga.

In the last couple of years, though, La Liga have committed themselves to seriously upping their game off the field of play. The league's administrators have launched an aggressive and proactive marketing campaign to narrow the financial gap, and international audiences are at the heart of their strategy.

Joris Evers, La Liga's chief communications officer, is open and forthright about the competition's lofty ambitions. "Our objective is to establish La Liga as the second most popular football league in every country around the world, always after the local league," he told BBC Sport.

"We're an innovative league that wants to be ahead of the curve. We are more than a football product - we are an entertainment and lifestyle brand. We're trendsetters when it comes to opening international offices, and all is done with an institutional, commercial and fan focus at heart."

As Evers notes, a key aspect of La Liga's global marketing strategy has been the opening of offices in nine countries, permanently staffed by a team of 44 delegates, with the aim of working closely with local clubs and authorities to develop a reputation as friendly allies, rather than greedy foreign invaders.

"What really sets us apart are the international delegates dotted around the world. It's an aggressive strategy that has helped La Liga grow its social media numbers to overtake rival leagues, and also allowed us to grow our television revenue and gain relevance as well as knowledge about international markets."

Although plans to stage January's league game between Barcelona and Girona in Miami were shelved after Fifa refused permission, other initiatives have included former Real Madrid and Liverpool winger Steve McManaman hosting a live screening of October's Clasico in front of 25,000 fans at the East Bengal Ground in Kolkata, while Indian cricket commentator Harsha Bhogle (over eight million followers on Twitter) is among the influential celebrities who have been chaperoned to Spain to enjoy a 'La Liga experience'.

Wu Lei is a key figure in La Liga's attempts to conquer the Chinese market

China: the most important market?

China, of course, is a hugely important territory in this marketing battleground: with its enormous population of 1.4 billion (double the whole of Europe), including a rapidly expanding middle class with sufficient disposable income to indulge in luxuries such as TV subscriptions, it has the potential to become the single most lucrative region for European leagues.

To give some context to the significance of China as a footballing market, it's eye-opening to note that many Premier League games attract a live British TV audience of around 500,000, a mere one-fiftieth of the 25 million who watched Espanyol v Valladolid in China.

On a more local level, Espanyol have already benefitted by receiving a significant influx of new fans from Barcelona's 70,000-strong Chinese community, and their games are suddenly gaining plenty of coverage in the Chinese sports media. The club is also expected to hold a lucrative pre-season tour of China during the summer, with Wu naturally taking centre stage.

However, the big challenge for the club - and for La Liga in general - is turning those new fans into permanent supporters rather than seeing them disappear whenever Wu happens to leave.

Overcoming the Premier League's deeply entrenched global dominance is not an easy task and it will not happen overnight, but La Liga will not fail through a lack of effort. And in one crucial country, at least, the Spanish top flight is making serious inroads thanks to the arrival of Wu.

"China is an important market and, of course, a great opportunity for us," said Evers.

"The passion for football in China is growing, so we want to seize this momentum. Wu Lei's impact is, without doubt, important. More and more Chinese fans are following La Liga, and we want to use this attention to promote the competition."

Occasions such as Saturday afternoon's derby - which will see China's national icon face Lionel Messi and co in a seriously competitive game in front of 90,000 fans rather than a fabricated pre-season friendly - are naturally viewed by the league as a golden chance to attract more new followers.

And if Wu is able to make China rejoice by breaching Barcelona's defence and scoring at the Camp Nou, it could prove to be one of the most significant goals in the modern history of sport business.