Cristiano Ronaldo and Lionel Messi: Is their era of dominance heading towards its end?
Seven weeks into the season, Cristiano Ronaldo and Lionel Messi have scored only three club goals between them.
The pair have dominated football for the past decade, with a combined 1,369 goals, 10 Ballons d'Or and nine Champions League titles.
But with Barcelona and Argentina's Messi, 32, suffering from multiple injuries already this season and Juventus and Portugal forward Ronaldo, 34, no longer winning golden boots, are we witnessing the beginning of the end of the pair's era of dominance?
Has the decline started?
Nothing lasts forever. This is the first time since 2005-06 they have scored fewer than five club goals combined by 30 September.
Last season was the first time in 11 years that neither won the Ballon d'Or - although Messi did win the recent Fifa player of the year award.
Messi has played 476 games in all competitions since the start of 2010-11, more than anybody else in Europe's top five leagues. Ronaldo is third on that list on 452.
But the Argentine has played a total of 90 minutes during his side's seven La Liga games and is already on his second injury of the season - although he could potentially return against Inter Milan on Wednesday.
While Messi has had problems throughout his career - he has only ever had one injury-free season - he usually does not miss too many league games.
Even if Messi plays all remaining 31 La Liga games, it will be the joint fewest he has managed since 2013-14. If he misses another three across the season it will be the fewest since 2007-08, before he entered his goal-a-game form.
He still had a phenomenal season last year, with 51 goals in 50 games helping him win the Fifa award. But only 120 minutes - and no goals - this season will be concerning to Messi fans.
The amount of games Ronaldo - who has also had an injury this season - has played has dipped each season since 2014-15, with his goal tally largely falling too.
Last season's 28 goals in 43 games would be great by nearly anyone else's standards - but it was his worst goalscoring season since leaving Manchester United.
It was the first time since 2011-12 he had not won or shared the Champions League golden boot. And he was only the fourth top scorer in Serie A - five behind a player two years his senior, Sampdoria's Fabio Quagliarella.
But despite the relative slowdown, there are still goals left in Ronaldo's legs - he has scored eight in as many games for club and country this season, including one against Spal on Saturday.
How long can they stay at this level?
Ronaldo can take comfort from the fact most of the top-scoring older players in recent years have been in Italy.
Since 2010-11, six players aged 34 or over have scored 30 league goals or more in Europe's top five leagues - and four of those have been Serie A players.
Luca Toni managed 56 Serie A goals for Fiorentina and Verona after turning 34, with Antonio di Natale scoring 54 for Udinese from the same age.
Francesco Totti managed 43 for Roma, with last season's golden boot winner Quagliarella scoring 30 and counting.
But only two players have scored 30 goals or more in a season (in all competitions) from that age - both in 2015-16. Zlatan Ibrahimovic hit 50 in his final season at Paris St-Germain, with Aritz Aduriz scoring 36 for Athletic Bilbao.
Could Messi and Ronaldo suffer burnout having both started young and after playing so relentlessly for so long? By the age of 23 Ronaldo had played 184 Premier League games (plus 25 in the Portuguese top flight), with Messi featuring 144 times in La Liga.
But of the six players to score 30 goals over the age of 34, only one of them had played 100 times in Europe's top five leagues by 23 - Totti with 150 Serie A appearances for Roma.
Claudio Pizarro played 62 Bundesliga matches by that age, with Quagliarella featuring 24 times in Italy's top flight and Aduriz only playing three La Liga games. Toni and Di Natale had yet to even reach the top flight, playing in Italy's lower leagues.
Messi and Ronaldo's figures are closer to those of Wayne Rooney and Michael Owen, who managed 201 and 168 Premier League appearances by 23.
There is a widely-held belief the pair suffered burnout from playing so many games so early - however both of their England careers had ended before they reached Messi's current age.
What other records are left to achieve?
Ronaldo and Messi have most of the relevant goalscoring records between them, but there are still more up for grabs.
Messi is the all-time top goalscorer in La Liga, Barcelona and Argentina history - with Ronaldo holding the records for Real Madrid, Portugal and the European Cup/Champions League.
Ronaldo is second on the La Liga list, with Messi second in the European Cup.
So what else is there?
Ronaldo is the second top scorer in international history with 93 - but remains 16 goals behind Iran legend Ali Daei. But four goals in his last match against Lithuania increased his chances of breaking that record.
He also needs one more European Cup/Champions League to equal 1950s-60s Real Madrid player Francisco Gento's record of six. That would also make him only the second player, alongside Clarence Seedorf, to win it with three different clubs.
Unlike Ronaldo, who won Euro 2016 and the 2019 Nations League, Messi is likely to retire without winning a senior international trophy. He won the 2008 Olympics, a youth tournament, but lost the 2014 World Cup final and three Copa America finals.
The 2020 Copa America and 2022 World Cup will surely be his last chances.
Ronaldo's goal against Spal on Saturday took him up to 604 club goals, one above Messi's 603. The pair are the joint all-time top goalscorers in Europe's top five leagues on 419. Ronaldo has 422 league goals, but his three in Portugal for Sporting Lisbon do not count as one of the top leagues.
So what are some other goalscoring records they could break?
Statistics for previous generations and smaller leagues are often difficult to confirm. A list compiled by unofficial statisticians RSSSF claims former Austria and Czechoslovakia striker Josef Bican is the top goalscorer in official games with at least 805 (some data is missing for one lower-league season). Including international goals, Ronaldo is on 697 goals - 108 off that mark - with Messi 25 behind.
If Ronaldo did play until he is 41, he would only need to average 16 goals a season to break that.
Romario (772), Pele (767), Ferenc Puskas (746) and Gerd Muller (735) are the only players to score more than Ronaldo or Messi.
Romario and Pele both claim to have scored more than 1,000 goals but those include goals in non-competitive games.
Uefa says the record for most goals in European leagues is Bican's 518 (with 500 in Czechoslovakia the record for a single league), with Puskas one behind on 517.
When will they retire?
"Messi will not be playing when he is 40," said Spanish football journalist Guillem Balague in a recent BBC Radio 5 Live show.
The Argentine's contract with Barcelona runs until 2021, although a recent report claims he can leave at the end of any season if he wants. He has often said he would like to play for boyhood club Newell's Old Boys in his Argentine homeland one day.
"He's 32 and for the first time ever I have started hearing stories of people close to Messi 'how about if he has only got two more years at Barcelona?'" said Balague.
"At the end of every season he decides whether he is fit or not. He's got in the back of his mind, perhaps the World Cup. His contract finishes in 2021.
"That extra year... does he play in the elite risking his body and his mind or does he step down and prepare himself for his last World Cup in 2022?"
Ronaldo has said on several occasions that he could play until he is the oddly specific age of 41, but in August he admitted he could retire at any time.
"Maybe I can finish my career next year," he said. "But I can also play up to 40 or 41."
Who could be the next Messi/Ronaldo?
Kylian Mbappe is the obvious candidate. The 20-year-old France star, who has already won more World Cups than Ronaldo and Messi combined, is the top scorer in Europe's top five leagues under the age of 23. He has scored 63 Ligue 1 strikes for Monaco and Paris St-Germain, an average of one every 104 minutes.
In all he has scored 102 senior goals, including 14 in the Champions League and 13 for his country.
The next top young goalscorer in Europe's top five leagues is Real Sociedad's 22-year-old Mikel Oyarzabal with 37, one every 290 minutes.
Bayer Leverkusen's Kai Havertz, who is joint sixth on the list with 26 goals, takes on Ronaldo's Juventus on Tuesday.
There are plenty of other young talented attackers around, including 16-year-old Ansu Fati, who has scored twice and set up a goal in 231 minutes for Barcelona. Atletico Madrid teenager Joao Felix scored 20 goals in last season's breakthrough season at Benfica.
Or how about 19-year-old Leeds-born Norway international Erling Haaland, who has scored 17 goals in 10 games for Red Bull Salzburg this season, including four hat-tricks?
By the time he was 23, Messi had scored 88 La Liga goals. Ronaldo had scored 54 in the Premier League by that age, but he was still being used as a winger and took a while to adjust to English football.