Bellingham has become a focal point for England both on and off the pitch, with his performances and demeanour often dissected by media and fans after a meteoric rise that has taken him from teenage prospect to one of the squad's leading figures.
The Real Madrid midfielder is a player fans and media seem to either love or hate, and his intense on-field emotions have sparked widespread debate over whether his behaviour stems from passion or ego.
There have been questions around whether he should start for England, who kick off the World Cup against Croatia in Dallas on Wednesday.
"I honestly couldn't speak highly enough of him," Henderson told reporters after England's training session. "I know a lot gets written in the media, and I find it hard to read sometimes, because I just know how big an influence he is on this team, how good a teammate he is off the field and what he gives us is just something really special.
"I think he really gives us the X-factor. He's had big moments in his career. He's a big-game player. He's got experience in tournaments, so he's a huge, huge player for us in this tournament."
While Bellingham's rapid ascent has meant increasing responsibility in major matches, Henderson was keen to highlight the contributions people do not see.
"If you ask any player in the group, they'll tell you how much of a good teammate he is, how well he trains," Henderson said. "I know he's young, but he's very mature in his head.
Controversial selection
Henderson was a controversial selection himself, with manager Thomas Tuchel choosing the Brentford player who turns 36 on the day of England's opening match over younger midfielders Cole Palmer, Phil Foden, Morgan Gibbs-White and Adam Wharton.
Asked about his role at his fourth World Cup, Henderson - who was left out of Gareth Southgate's squad for the 2024 Euros - said Tuchel told him "to be myself, regardless of how much I'm playing, whether I'm playing every game, whether I'm not playing as much, just to be myself and enjoy being back in the squad."
Croatia's squad will feature Luka Modric, who at age 40 is playing in his fifth World Cup.
"I think his career speaks for itself," Henderson said. "He's a top world-class player, so hard to play against. Hopefully, he doesn't perform as well as we know he can against us, but I haven't seen him have a bad game yet, so it'll be a difficult test, of course, for whoever plays in midfield."
Henderson's inclusion in Tuchel's squad made him the first Englishman to be selected for seven major tournaments.
"Whether you're my age or whether you're 25, you never know when the last one is, to be honest, which is why you've got to treat every one like the last one," he said.
Follow England's opener with Flashscore.
The 2026 World Cup will be held from June 11th to July 19th in the United States, Canada and Mexico. The tournament will feature 48 national teams and will be played in 16 modern stadiums.
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