It feels slightly odd discussing the "out of form" Harry Kane. A couple of weeks ago, he showed off the World Cup Golden Boot at Wembley as just the second English player to win that trophy after Gary Lineker, who claimed it in 1986. He's scored twice in five league games this season: not mind-blowing, but not cause for panic either. One of those goals was at Old Trafford.
But watching him this season shows that something isn't right. The problem seems clear but the cause slightly less so. It could be just a typical loss of form that happens to any striker. It could be luck. It could be something that we don't know about.
Or it could be that he's simply exhausted, and there is a real danger here that football is flogging its brightest talents.
Last season Kane played in 37 of Tottenham's league games, starting 35 of them. He missed one match with a hamstring injury and came off the bench in two. He played the full 90 minutes a total of 26 times and the earliest he was taken off, when he didn't have an injury that prevented him from continuing, was the 75th minute. Throw in seven Champions League starts and four FA Cup games, followed by an emotionally and physically draining World Cup in which Kane played 573 minutes -- of players from the Premier League's "big six" teams only Kieran Trippier, Dejan Lovren and N'Golo Kante played more -- and you get quite a workload.
He's not the only one, either. Mohamed Salah has looked a touch off the pace so far this season, perhaps partly as a knock-on from the shoulder injury sustained in the Champions League final: again, he hasn't been terrible but at the elite level you only need to be a few percent below your best to be knocked off your stride. Eden Hazard's form has been excellent but even he was excused from Chelsea's Europa League group stage opener after telling Mauricio Sarri he was tired.
Since the start of the 2017-18 season, Kane has played 5,615 minutes over 67 games. Salah has played 5,251 minutes over 71 games, with Hazard notching 5,208 minutes over 72 games.
Simply put, the Premier League's elite players are not given time to properly rest. Their schedules are relentless. Last summer Kane had all of a week between Tottenham's last game and joining up with the England squad for their pre-World Cup preparations. Then, according to Mauricio Pochettino, he was back at the Spurs training ground two days after returning home.
Resting during the season is almost out of the question. Hazard took a sensible decision to warn his manager of his fatigue but it's only a few days off and he's in a good position to feel comfortable asking: given his blistering form and having been hailed as the best creative player in Europe by Sarri, he has more leverage to take a breather. Kane and Salah, perhaps not going so well, may try to push themselves further to get back into form.
Beyond simple tiredness, a lack of rest is also a danger for injuries. Pep Guardiola certainly subscribes to this theory: after Kevin de Bruyne (63 games last season and 540 minutes logged for Belgium in Russia), picked up a knee injury that could rule him out for three months, the Manchester City manager said: "My opinion is that when you ask a lot of the players, over more than 11 months, then after he comes back, this [injury] can happen.
The risks are definitely there.
"Almost certainly," says Ross Preston, formerly a fitness coach at several Football League clubs and currently an advisor to Bupa Health Clinics. "This fatigue can lead to injury, hormonal disturbances, illness and psychological effects. This is why sport science departments are closely monitoring each player's stats and vitals and can actually spot the signs [of trouble]... they can address [them] before the fatigue or illness affects the player.
"Most commonly, the hamstrings and anterior cruciate ligament (ACL) are prone to injury. A fatigued musculoskeletal system will display a decrease in motor coordination and force production, leading to a lack of eccentric strength -- decelerating -- when running, jumping or changing direction."
Put simply: if you're tired, you've got problems.
Some players handle these issues better than others. But despite the remarkably high levels of fitness planning, nutritional advice, physiotherapy expertise and recovery, these are just human beings, fragile and susceptible to damage.
Yet this could be an overreaction: once a player gets into the season, a summer at the World Cup might not be an issue.
"I don't think that lasts long into the season," said Crystal Palace manager Roy Hodgson, when asked by ESPN if he was concerned about the fatigue players could suffer from after their summer exertions. "I think if anything the question is not whether the fatigue will kick in and hurt those players later on, rather a case of whether they will find their real match fitness in the first moments of the season.
"I don't think the World Cup carries that sort of burden deep into the season."
It's entirely possible that Kane turns his season around this weekend. Salah too. Hazard could continue his brilliant form. But players are being encouraged to push themselves and it's perceived as a virtue to do so. Football has to be very careful that they're not pushing them too hard.
"It's part of the game for the players: it's normal, they don't rest," said Guardiola. "It's a tough season, with short recovery times. They [the football authorities] say 'let's go' and we are in the competition.
"Human beings have a limit."