Jude Bellingham turns 21 on Saturday and is already a seasoned international with England, a Champions League winner with Real Madrid and an undisputed member of the new wave of superstars ready to dominate a post-Lionel Messi/Cristiano Ronaldo football landscape. He is the archetypal box-to-box, goal-scoring midfielder, a supremely confident and rounded youngster who projects maturity beyond his age and is nothing short of a marketing agency's dream. Golden Boy? That's Bellingham all over.

But for the first time in his prodigious career, the storm clouds are gathering. Less than a month ago, after helping Madrid win the Champions League for a record 15th time in a 2-0 win against former team Borussia Dortmund in London, Bellingham was being billed as the favourite to win this year's Ballon d'Or after bagging 24 goals and 13 assists from his 45 games. Yet after a poor run of performances for England at Euro 2024 in Germany, the closest he might get to the trophy is a birthday cake made in its image.

Although he scored the only goal of England's 1-0 win against Serbia in their opening game of the tournament, Bellingham contributed little during the subsequent fixtures against Denmark and Slovenia -- both draws -- and goes into Sunday's round-of-16 tie against Slovakia with doubts over his place in the team.

After enduring the frustration of 90 goalless minutes against Slovenia in Cologne, Bellingham said he was "absolutely dead" -- a worrying admission of fatigue at not even the halfway stage of Euro 2024. When asked by reporters after the Slovenia game about Bellingham's performances in Germany and whether he wants more from the player, England coach Gareth Southgate hinted at his dissatisfaction with a guarded response.

"I will have those messages with [Bellingham] rather than plaster them over the papers," Southgate said. "It's about the team. We have to play as a team at all times."

Wayne Rooney, the former England captain who carried similar pressure to Bellingham as a young star at major tournaments, says that the Real Madrid midfielder's frustrations are now impacting on his performances.

"For me, he's looked very frustrated [at Euro 2024]," Rooney told the "Football Daily" podcast. "I've been there -- exactly the position he's in -- and even in the game [against Slovenia], you saw him throwing his arms up in the air.

"As a talisman for England and Real Madrid, I haven't heard him in speak. What is the reason for that? As one of the iconic players now for England in the squad, he should be fronting that. That tells me that he's probably not quite right in the tournament."

The debate around Bellingham is not one that many expected to be taking place right now, but there might also be mitigating factors behind his inability to shine so far.

He has been troubled by a shoulder problem since sustaining an injury last November -- an issue which forced him to miss four Madrid games -- and an ankle injury in March ruled him out for three weeks. The shoulder injury continues to affect Bellingham, as shown by the heavy strapping he was wearing during the Slovenia game which he revealed after removing shirt at the final whistle.

Darren Burgess, the FIFPro senior adviser on player workload, told ESPN at the start of the tournament that Bellingham had already clocked up 18,571 minutes in senior football. That figure now stands at 18,837 after completing all but four minutes of England's three group games.

For context, by the time they were 21, Rooney had registered 15,481 minutes for club and country, while Steven Gerrard had managed 7,034; David Beckham had registered just 3,929 minutes.

Perhaps Bellingham's injuries and physical exertions are catching up with him at precisely the time when most is expected of him at Euro 2024. One source told ESPN that Real Madrid coach Carlo Ancelotti regards the selfless energy and team ethic of Uruguay midfielder Federico Valverde as being crucial for Bellingham to play with such freedom in Spain. It goes without saying that Southgate's squad does not possess a player with Valverde's attributes, so Bellingham is struggling to be the force he is with his club.

"Valverde is the legs of the Real team," Stewart Robson, former Arsenal midfielder and ESPN La Liga analyst said. "He doesn't just do the job for Bellingham, he does it for the whole team. He helps out Dani Carvajal at right-back, allows Vinícius Júnior and Rodrygo to focus on their attacking roles and is generally a vital cog for Real. England don't have anyone like Valverde. The only one who provides the same kind of defensive cover is Kyle Walker because of his pace."

Reliable defensive cover is crucial for Bellingham, especially when he plays in the No. 10 role and spends his time focusing on the attacking third rather than his defensive duties as a midfielder.

Going into the tournament, Southgate told ESPN he wanted to exploit his attacking qualities and said that Bellingham is "one of the players that needs to be in the team."

"With Dortmund he was a more attacking-minded No. 8," Southgate said. "There's moments he's played as one of the double-No. 6 and he's done that with us a couple of times early on. But he's a player that you need to allow the license to go forward and with Madrid he's had a huge amount of freedom, where he's been a false No. 9 most of the season. He has been an attacking player and had a devastating impact on games through doing that.

"We're probably seeing him as a more advanced player than we were two years ago when you're still looking at everything that he might be. Of course, when you're playing in a certain way every week with your club, to then do something completely different when you come with the national team is more challenging. But he's without a doubt one of the players that needs to be in the team and it's getting the right balance of where all those players fit and what's the best balance for the whole group."

Southgate has clearly still to find the balance that England need in order to exploit Bellingham's strengths rather than expose his weaknesses.

Sources have told ESPN that there has been a discussion internally about whether the "Phil Foden and Bellingham" conversation should become Foden or Bellingham, while it has been pointed out in internal video analysis meetings that the pair have often occupied similar spaces when attacking. However, Southgate has sidestepped questions about whether he would have to sacrifice one of the two in pursuit of a more effective team.

England's inability to progress the ball quickly through midfield has affected all of their forward players at Euro 2024, and Bellingham is no exception. Southgate hoped that Trent Alexander-Arnold's passing range and vision would help give Bellingham, Foden and Bukayo Saka the ball early enough in space to cause opponents problems, but England have been ponderous in possession, something Southgate acknowledged both in personnel and tactics by eventually switching out Alexander-Arnold for Conor Gallagher and tweaking his 4-2-3-1 system to 4-3-3 with the ball in their final Group C match against Slovenia.

Part of the idea was that Gallagher could help improve England's press and so they would turn the ball over higher up the field, allowing England's front four to take advantage of quicker turnovers in advanced areas. That would help negate England's issues in build-up, but the tactical change didn't work. And as Southgate rolled the dice by introducing Cole Palmer and then Anthony Gordon late in the second half, Bellingham found himself out on the left wing at times so Foden could drift more centrally, and then on the right when Palmer looked to briefly affect the play on that flank.

None of it suited him. Bellingham's irritation has been evident, even in the Serbia game when midway through the second half he went to press on his own, was easily bypassed and visibly recoiled at the lack of help.

"He's giving it his all, 100%, I don't think that's the problem," Rooney said. "You want players demanding more from their teammates and I think that's what he was trying to do. "It's not a criticism, it is a compliment in some ways, but you just don't want that to boil over to the point where he might pick up a silly red card."

Bellingham's temperament, and not just his overall performances, has been a cause for concern in Germany. He has allowed himself to become embroiled in pushing and shoving with opponents in each game so far and has been noticeably vocal towards officials. And Robson, who has studied Bellingham throughout his first season in LaLiga, believes that his attitude has changed.

"There was a difference in him in the second-half of the season compared to the first," Robson said. "You could sense a change in attitude. "Early on, he was all smiles, loving life, chasing back, working hard and scoring goals. But after Christmas, he entered a sulky phase. He would be tackled and then spend three seconds on the floor, complaining to officials, acting as though the world was against him and we've seen that in Germany too. He basically went big-time. There was so much talk in Spain about him being as good as Zinedine Zidane and his whole attitude changed. He stopped working as hard."

In Bellingham's defence, however, the change identified by Robson took place after the first shoulder injury, so was that a factor in his declining performances and change of attitude?

"That's possible," Robson said. "If you're carrying an injury and playing through pain, you don't want to make so many challenges and you struggle through games, so if that happens, there's only one way your performances will go."

Meanwhile, sources have told ESPN that Bellingham's elevation to England's four-man leadership group for these finals, alongside Harry Kane, Declan Rice and Kyle Walker, caused a degree of surprise among some connected to the camp. Southgate's explanation that he wanted a conduit to the younger element of the squad was the justification and Bellingham's appointment was greeted positively by his teammates, but it has come early his career.

Then again, so has everything he has achieved to date. Despite his elevation to the England squad's group of senior figures, Bellingham, as identified by Rooney, has yet to speak to the media beyond the English FA's in-house Lion's Den channel, so his views on his own performances have yet to be disclosed.

But, speaking to Lion's Den after the Slovenia game, there was an acknowledgement that England have not performed to expectations.

"You can play at a level that's not your normal or not your best, but the important thing when you're wearing this badge and this shirt is that you're representing them [supporters] and you don't give up," Bellingham said. "I know there's a lot of negativity outside the camp and the stadiums, but I always feel when we get in the stadium, it's so different. I think it's important, as teammates and as a team, we remember that the ones in the stadium are the ones who are going to give us the energy, so don't worry about those who aren't there."

Bellingham is there, but he is also yet to arrive in the tournament. With the knockout stages now here, England really need Bellingham to finally turn up.

(Additional reporting by Alex Kirkland)