Phil Foden turned 21 on Friday, the day before he will play for Manchester City in arguably the biggest game in his boyhood club's history.

For all Foden's understated public persona and the unfussy way he goes about his business on the field, such a high-stakes landmark has felt inevitable since he emerged as a precocious and remarkably fully formed talent four years ago.

"I don't have words. I would like to have the right words to describe what I saw," Pep Guardiola told reporters after Foden sparkled in an International Champions Cup friendly against Manchester United in Houston, Texas.

"You are lucky guys, believe me, you are the guys who saw his first game in the first team at Manchester City. I've not seen something like I saw today for a long time. His performance was another level."

It is a level at which Foden has largely remained, meaning Guardiola frequently had to resist clamour to give the youngster more game-time. Over the past six months, he has become one of the first names on the team-sheet, so that is no longer a problem.

Ilkay Gundogan, the only City player to have previously featured in a Champions League final, when Borussia Dortmund lost to Bayern Munich in 2013, expects Foden to take Saturday's encounter with Chelsea at Estadio do Dragao smoothly in his stride.

"Phil has become one of our main players throughout the season," Gundogan said. "He's doing incredibly well, he improved in so many details of his game, mainly in taking the right decisions at crucial times.

"For such a young age it is really impressive. I wouldn't recommend him to change anything from what he's done over the past few weeks. He is one of the game-changers for us and he can be one on Saturday."

Next on the horizon will be the European Championship, where Gareth Southgate will have designs on Foden being a game-changer for England. It could be a momentous few weeks for the quicksilver attacker, so it feels like a very good time to have a look at some of the numbers – from one to 21 – that got him to this point.

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Foden has scored 31 times for City in all competitions but few have been as important as goal number one in the Premier League. Starting for just the second time in the top-flight, he showed an aptitude for timing runs into the box to nod home Sergio Aguero's header across goal against Tottenham in April 2019. It was the only goal of the game, coming four days after Spurs knocked City out of the Champions League in dramatic fashion and at the business end of a knife-edge title battle with Liverpool, where Guardiola's side prevailed by a point, 98 to 97.

In the book Pep's City by Pol Ballus and Lu Martin, Foden was described as "lighting up the darkness that engulfed the first team squad in training" after the Champions League heartbreak.

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Foden probably overhauled that Spurs goal twice in the eight days when he made it two winning goals in two against Borussia Dortmund in this season's Champions League quarter-finals. First, he struck in stoppage time for a 2-1 win in Manchester after Marco Reus equalised for the visitors, and then he smashed home from a short corner to spark frenzied touchline celebrations with Guardiola as City won by the same scoreline at Signal Iduna Park.

It meant Foden was the second player under the age of 21 to score in both legs of a Champions League quarter-final after Kylian Mbappe, who did so for Monaco against Dortmund in 2017. Considering the prolific start to Mbappe's career in Europe's elite club competition and his exclusive use as a forward, Foden shapes up pretty well by comparison. In 1,544 minutes of Champions League football he has 11 goal involvements (six goals, five assists). After 1,540 minutes in the tournament, Mbappe had 17 (12 goals, five assists).

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The 2020-21 season saw Foden make it three Premier League winners' medals for his personal collection. He has played a far bigger part this time around. All of his five appearances in 2017-18 came from the bench. When City retained the league the following year, that vital winner versus Spurs was his only goal involvement in three starts and 10 outings as a sub.

This time around, Foden played in 28 of City's 38 matches, starting 17. His final-day goal against Everton took his Premier League tally to nine, alongside five assists.

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After his first trip away with the England senior side ended in ignominy last September, Foden needed something special to fire himself back into the Euro 2020 reckoning upon his return. He duly delivered in November with a first international goal against Iceland at Wembley. His second followed four minutes later.

England 4-0 Iceland

At 20 years and 174 days, he was the youngest England player in history to score more than once in a game at Wembley.

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Foden has truly excelled since making the left-wing spot his own at City this season. When Aston Villa arrived at the Etihad Stadium for a thrilling encounter in January he was in full flight. Five shots and six chances created over the course of a 2-0 win made him the youngest player to register 10+ shot involvements in a game under Guardiola at 20 years and 237 days.

He overtook a certain Lionel Messi, who managed the feat against Sporting Gijon at 21 years and 89 days in 2008 – during Guardiola's first season in charge of Barcelona – giving a timely reminder that Foden has come under his tutelage at an earlier stage of development.

"I didn't meet Leo Messi at 17 years old like when I met Phil. And at that age, I never saw a player with this potential," Guardiola told BT Sport. "But you have to see them on pitch in the biggest stages, and he is a guy who is comfortable, who loves to play."

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Following his first pre-season tour with the senior City squad, Foden served loud notice of his potential by standing above his peers in England's 2017 FIFA U-17 World Cup win. Featuring in all seven of his country's games in India, scoring three times, including two in the 5-2 final victory over Spain, Foden was named player of the tournament.

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The prizes have continued to stack up for Foden, with this season's Premier League being a major trophy number eight in City colours. Alongside three league titles are four EFL Cups in succession and the 2019 FA Cup, where he scored three times over the course of the competition to help complete a domestic treble.

He also starred in Community Shield triumphs against Chelsea and Liverpool in 2018 and 2019 respectively, but we're not counting those as major honours. Don't tell Pep!

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Although a knack for scoring crucial goals has been a defining feature of his early career, Foden's reputation is built upon his exceptional creative skills. In 2019-20, as his prominence in Guardiola's plans was increasing, he supplied nine assists from 41 chances created, placing him fifth overall for City in all competitions as Kevin De Bruyne led the way with an absurd 22 assists from 177 chances created.

This season, De Bruyne is still out in front (18 assists, 111 chances created) but Foden is up next on 10 assists. He has created 75 chances overall, 13 of which have been classed as big chances by Opta.

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But back to those goals, because this is certainly an area where he has shifted rapidly through the gears. In 2020, Foden completed the calendar year with 11 to his name. He already has the same amount in 2021 heading into Saturday's final.

"I am feeling really confident in front of goal. Every chance I get, I feel like I am going to score,” he told Sky Sports last year, having put his time to good use during lockdown..

"I was in okay form before we broke up, if I am honest, but I have come back flying. Through quarantine I tried to work on some things like one-on-ones and come back stronger."

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Much like the goals and assists stats, another Foden figure that is likely to climb rapidly over the coming months and years is the fact he has only started 12 competitive games against the other members of English football's 'big six', including Community Shield meetings with Chelsea and Liverpool.

"Now Phil is demanding other things from the manager," Guardiola said in his BT Sport interview with Rio Ferdinand. "Before, play five minutes, 20 minutes he is happy; play Carabao Cup, he is happy. Now next season, don't play him in a Champions League game, see what happens. He is another status, he is going to demand."

This status looks like being beneficial to Guardiola, given Foden's overall record in City colours, which reads: played 123, won 100, drawn 10 and lost 13. In matches he has started this season, the English champions are W30 D3 L2 and W17 D3 L5 when Foden has been on the bench or missing, a win percentage drop from 85.7 to 68.

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Foden's enhanced standing means he is now less likely to be a victim of the dreaded Guardiola "overthink". This is, of course a disingenuous tag attached to a coach who gets so deeply into his work he has spent press conferences eulogising over the terrifying qualities of Nathan Redmond and Sam Vokes. If he overthinks, he does it every single game, for better and for worse.

However, plenty of City fans will dread an unusual team selection in Porto, such as the 3-5-2 that collapsed in a heap against Lyon in last season's quarter-final. Foden had started in the previous round's second leg against Real Madrid as a false nine and had 14 goal involvements for the season (eight goals, six assists), but looked on as an unused substitute in Lisbon. His blossoming is one of the reasons the City team sheet should be more predictable this time around.

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Having led his country to glory in India, Foden graduated to England Under-21 level, where he was similarly dazzling over the course of 15 caps and four goals.

He scored both in a 2-0 win over Kosovo and curled in a wonderful free-kick in Albania. The Young Lions flopped badly at Under-21 Euro 2019, but Foden's deft solo goal in a 2-1 defeat to France marked a rare high point.

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Only Gundogan has managed more than Foden's 16 in a season where City have shared the goals around. Although plenty would back him should a key opportunity fall his way at Estadio do Dragao, there is room to become more clinical.

Phil Foden xG 2020-21

In terms of expected goals overperformance among City players to have scored 10 or more times this season, Foden is in a good place, over-performing his xG of 10.88 at a similar rate to Gundogan (17 goals, xG 11.69).

A shot conversion rate of 16.2 puts him below Gundogan, Ferran Torres and Gabriel Jesus within this group of players, while he has scored seven and missed eight big chances (46.7 per cent).

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Foden's early breakthrough at City meant he achieved a cluster of age-related records. At 17 years and 283 days, he became the youngest English player to feature in a Champions League knockout match when Guardiola shuffled his pack thanks to a 4-0 first-leg advantage over Basel in the 2017-18 round of 16.

The next season, the cherished moment of Foden's first senior goal arrived, at the start of one of those triumphant EFL Cup campaigns against Oxford United. By now 18 years and 120 days, he was the first City player to score for the club having been born since the turn of the millennium.

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When the following season's competition concluded, at a full Wembley a couple of weeks before the pandemic took hold of the UK, Foden was a surprise starter and man of the match at 19 in a 2-1 win over Villa.

Along with an assist for Sergio Aguero's goal, he completed 90 per cent of his 41 passes in the opposition half, made 70 touches overall and won seven out of 10 duels.

He was all over the contest and his prominence has increased exponentially since that point. This February, when City roared to a 4-1 win at Liverpool – their first away win in the fixture since 2003 – Foden bent the game to his will and crowned victory with a blistering individual strike. At 20 years and 255 days, he was the youngest player to score and assist in a Premier League game against Liverpool at Anfield.

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And now, to another big game. The biggest.

The day after he turns 21, Foden will take all of this prodigious talent and elite experience and try to build upon it in pursuit of European glory. And we all get to watch.

"You are lucky guys, believe me."