For England, the thought is frightening but very real. This could be Harry Kane's final World Cup.
"It could always be my last because you never know what happens in football," the Three Lions captain said earlier this month. "But you know what I'm like, I want to play for a long, long time."
Turning 33 this summer, this is unlikely to be Kane's last tournament with England, having already expressed his ambition to play at the European Championships on home soil in 2028.
But given his age, this tournament feels particularly big for Kane on an individual basis. There are no guarantees he will appear at this tournament come 2030, when he will be almost 37.
This is not just potentially his last dance at the World Cup. It is probably the best chance he will get for the Ballon d'Or.
England have not had a Ballon d'Or winner since Michael Owen in 2001 - and Kane has a real chance to end that run. He comes into the tournament as not just arguably the best player in the world - but the best version we've ever seen of him.
His 67 goals for Bayern Munich and England this season - including 11 in as many 11 international games - is not just the highest season's goal tally of his career, but the most any player has managed in the season going into a World Cup.
"[The World Cup] is coming off the best season I've ever had," he said on the eve of the tournament. "I've been scoring a lot more goals that I have in any previous season.
"But physically and mentally, the way the season ended for me was great - winning the league and the cup final, scoring three goals there. That gave me even more momentum coming into the camp with the boys."
Kane has six more goals than Cristiano Ronaldo managed in 2013-14, before the Brazil World Cup. Ronaldo did not back that season up with international glory, but it was still enough for Ronaldo to win the Ballon d'Or, having won the Champions League and Copa del Rey that season. He also started the following season on fire.
Translating this form from season to summer - especially at the end of a long season - is still a huge challenge for Kane.
Take Euro 2024 as an example. Kane had a superb debut campaign at Bayern, scoring 44 goals across all competitions. But come the latter stages of the Euros, the England captain was exhausted - so much so that Gareth Southgate took him off in every game from the quarter-final onwards.
Thomas Tuchel has played down concerns that Kane will be arriving tired. He said: "Ideally we can take some minutes off him, but if the matches are close, do we really do this? Do we take our main goalscorer, our captain off? Maybe not.
"The most important thing is the shape Harry is in. He's in top shape, he is ready to go. He's used to high pressing, high intensity in the opponent's half with Bayern Munich."
Kane added ahead of the Croatia game: "From a physical point of view, I feel in great shape in the training sessions and matches we played.
"Throughout your career, you need a lot of things to go your way and fall into place at the right time. It has for this tournament. It's one of the best opportunities we all have as a team to win it."
And Kane knows that - despite winning every domestic trophy possible with Bayern this season - a good World Cup ould be required to put him in the Ballon d'Or picture.
"I'd probably say I'll be up there for sure," replied Kane about his chances if he achieves glory with England this summer.
"With the season I've had, I think with winning the three trophies, the numbers I've reached, I think I'll be in that conversation. If I win the World Cup on top of that, you would imagine it would be one of the England players.
"When you look at some of the past winners of the Ballon d'Or, for sure it comes down to the big games, the big tournaments, and you add that on top of what I've achieved this year, I think I'll be up there."
Kane has never finished higher than 10th in the Ballon d'Or voting dating back to 2017. But now is not the time for top 10s. This is about being No 1.
Your Site News' Rob Dorsett in Kansas:
SIxty-four goals in 57 matches is nothing short of extraordinary. He has scored 146 goals in 147 matches in the last two seasons. That is staggering. He will equal David Beckham's England cap figure against Croatia with 115. That is history.
England's all-time leading goalscorer has 79 international goals - 12 more than the rest of the entire squad put together.
I don't use these statistics lightly. They matter to Kane. Like Cristiano Ronaldo and Lionel Messi (whom Kane both idolises and compares himself to), England's captain chases landmarks. He collects records like Golden Boots.
His importance for his country is unarguable. England cannot win the World Cup without him, and without him on top form.
Thomas Tuchel has said two things during the build up to this tournament which sum up where Kane is at. Firstly, while the rest of us worry about an over-reliance on the captain to get the goals, Tuchel does not.
"Why would Argentina not rely on Messi, or Portugal not rely on Cristiano Ronaldo?" he said. "In the absence of Harry Kane, we don't have the same threat. Bayern Munich in the absence of Harry Kane has not the same threat. No team in the world has the same threat."
Secondly, Tuchel says Kane is in the best physical shape he has ever known him. And don't forget, while watching from afar for most of his career, Tuchel worked closely with him at Bayern Munich, and so has seen him up close and personal on a daily basis.
It certainly seems true that Kane is going into this World Cup in a much better place than he was two years ago, when his three goals still helped England to a Euros final and earned him a joint share of the Golden Boot in Germany.
Then, even though he denied it, it was clear when you watched him daily in training, and off the ball in matches, that he was really struggling with a back injury. I would often see him strolling around the pitch rather than running. He looked stiff, lacking mobility. In pain.
Now, see him in the flesh and he is glowing. He is lean. He is sprightly. He is smiling. And he said in the news conference ahead of this game that he feels like all the jigsaw pieces have fallen into place at the right time for him. Fitness, form, belief - all maxed out.
And when I interviewed him after the 1-0 win over New Zealand in Tampa - a win where, inevitably, it was his goal that sealed it - he was more bullish about his own form and fitness than I had ever known him.
"I feel as good as I've ever felt, and it can't come soon enough. I'm just excited for this thing to get going."
We are too, Harry. Please stay fit.
