Premier League players can make millions from their football careers but one forgotten former Arsenal star has enjoyed arguably far greater success after it.
Frenchman Mathieu Flamini made 246 appearances for Arsenal across two separate spells from 2004 to 2008 and later 2013 to 2016.
It was just after he left the Gunners the first time for AC Milan in 2008, that he and his economics graduate business partner, Pasquale Granata, founded the company 'GF Biochemicals' in the hope of revolutionising the energy industry.
The 39-year-old retired in 2019 and the biochemical entrepreneur has found great success with his other passion in his life outside of football.
As reported by the Sun, the company some 15 years after it was set-up, is claimed to be worth £21billion - some 40 times more than Cristiano Ronaldo's staggering £500m net worth.
After he and Granata founded the company in 2008, they invested millions in research, trials, infrastructure and employee fees, in the hopes of producing levulinic acid - a synthetic oil substitute made wood and corn waste.
Their company in 2015 became the first on the planet to be able to mass produce the acid, which can be used to replace oil in the manufacture of pharmaceuticals, plastics, cosmetics and more.
Flamini told the Sun at the time: 'We are pioneers. We are opening a new market and it's a market potentially worth £20billion.'
It led to him being named as one of the People of the Year in 2015 by the NME.
The Frenchman, now CEO of the company, told Sifted in an interview: 'As a child I had two passions: football and sustainability. I grew up in Marseilles near the sea, and was aware of the environmental questions around ocean plastics and chemical pollution from a very young age.'
He kept his company quiet from his team-mates, family and friends for the first five years that it was in his place as he 'didn't know which direction the business would go in' and that there was more pressure on him because he was a footballer.
In an interview with the Sunday Times, he added: 'Sometimes I had to go to the training ground dressed in a suit, and when you go to training most of the time you wear tennis shoes, a tracksuit and a T-shirt.
'So with the boys we were all laughing, they were making jokes — "Oh, you’re the best businessman!" But obviously biochemicals is not always what we talk about in the dressing room.'
The 39-year-old now claims that he's joining the younger generation, such as Greta Thunberg, in setting up the future.
Flamini added: 'Now the question is when do I not work. When you’re an entrepreneur you have to be dedicated and you don't count the hours. I’m not working when I sleep, but for the rest of the time I’m available.'
'I feel like I’m part of this effort of the younger generation like Greta Thunberg that’s setting up the future.
'Although at the age of 15 (when Thunberg staged her first protest outside the Swedish parliament) I can guarantee you I was not in the street fighting for my future.'
Since his company became the first on the planet to be able to mass produce levulinic acid, they have continued to grow.
Back in 2016, they acquired US company Segetis as they continued to look for green alternatives to oil.
Next to a graphic of the two businesses' logos, Flamini tweeted at the time: 'We founded GFBiochemicals to find green alternatives to oil. The acquisition of the American company Segetis takes us closer.'
As per the Sunday Times, as of May this year the company employed 50 people across its global offices: a headquarters in Paris and R&D facilities in the Netherlands and the United States.
It is not the only thing that Flamini has stuck his teeth into, with the Frenchman invested in 'seven or eight' startups as of last year, according to Sifted.
He was also part of a team that created BIOCIRCE (Bioeconomy in the Circular Economy) - Europe's first master's degree dedicated to promoting bioeconomy education.
Flamini also co-founded the BioJournal - the world's first e-magazine which is dedicated to eco-sustainability.
On the side of that, he also sat on the Environmental Olympic Committee for next summer's Paris 2024 Olympics and celebrated July 14 - French National Day - with president Emmanuel Macron.
He regularly shares updates on what he's doing on his social media, posting pictures where he 'pledges to protect the ocean'
Reports of the valuation of the company suggest its worth is 40 times more than Ronaldo.
This is despite the Portuguese star being on a salary worth £173m-per-year at Al Nassr, plus all of his significant sponsorship deals - with endorsements with the likes of Armani and Tag Heuer.
He is also said to have a staggering lifetime contract with sportswear giant Nike.
Ronaldo, like Flamini, has also invested outside of football with a number of businesses.
He has a number of hotels named Pestana CR7 - in Lisbon, Madeira, New York, Madrid and more.
In late 2016, he expanded into gyms in a partnership with US health company Crunch, with the first outlet under the 'CR7 Fitness' name opened in Madrid. While in 2019 he launched a hair transplant clinic in Spain called Insparya.
Flamini's wages during his football career were nothing like Ronaldo, earning around £140,000 per week during his two seasons at AC Milan.
It's claimed that in biochemicals that estimates put the value of the market at more than £64billion.
Despite reports of the value of the company, Flamini is keeping it quiet as to its actual worth.
He told the Times: 'Of course I’ve been asked a few times about the value of the company, but this is something I’ve never directly commented [on].
'The company is a private one but we don’t really communicate about the value. Obviously the market opportunity is a big one. But my main goal is — I want to make this business successful.'