Over the last decade, and a little more, the Champions League has seemingly been Lionel Messi and Cristiano Ronaldo’s playground at times.
In fact, in the 16 seasons since Ronaldo made his debut in the competition proper for Manchester United, the iconic duo have finished as winners on nine separate occasions.
What’s more, in every year since 2006/07, one or the other has been the competition’s top scorer. They even shared the honour - with Neymar - in 2014/15.
That record has seen them amass a combined 242 goals to sit well clear as the Champions League’s two highest scorers of all time. Ronaldo currently leads the way with 128 to Messi's 114.
But as we enter the 2020s and the pair edge ever closer to the end of their illustrious careers, it begs the question: who will take on their mantle in the world’s greatest club football competition?
Several have been tipped to succeed them over the years but few have come close to producing numbers even comparable in a single season, never mind over a prolonged period.
Neymar was perhaps championed more than anyone and there was a period during his time alongside Messi at Barcelona that it looked like he might get to their level.
But if Paris Saint-Germain’s Brazilian superstar is no longer considered capable of breaking the Messi-Ronaldo duopoly, he most certainly has a team-mate who could.
Kylian Mbappe is just 21 years old and already has three Ligue 1 titles and a World Cup winner's medal to his name.
Even after such a remarkable slew of early successes, the Frenchman's potential for further on-pitch development remains frightening.
And what's more, Mbappe's undeniable talents are seemingly backed up by the requisite temperament to deal with the pressure of becoming the sport’s leading light over the coming years.
Next on the former Monaco man's hitlist is the Champions League, where Borussia Dortmund now lie in wait in the last 16.
The German giants boast the teenage star who has taken the competition by storm this season and sits second in the scoring charts – Erling Braut Haaland.
The two go head-to-head on Tuesday 18 February, exclusively live on BT Sport, in a must-watch encounter that not only pits two of Europe’s most exciting teams against one and other, but also two of its most promising rising stars.
Nineteen-year-old striker Haaland, the son of former Nottingham Forest, Leeds United and Manchester City midfielder Alf-Inge, had a whirlwind 2019 that saw him truly rise to prominence on the European stage.
Long touted as a future star for his goalscoring exploits in his native Norway, Haaland claimed wider recognition when he scored nine in an astonishing Under-20 World Cup showing against Honduras in May.
That was just months after he had moved to Austrian Bundesliga side Red Bull Salzburg and having had six months to settle in, the former Molde forward began this season on fire.
Coming into his Champions League debut against Belgian champions Genk in September, he had 11 goals in just seven league games and had already notched three hat-tricks in all competitions.
He didn’t have to wait long for his fourth. He became the first teenager since Wayne Rooney to bag a treble on his Champions League debut, with all three coming in a devastating first-half display against the bewildered Belgians.
That was just a taste of what was to come, as Haaland went on to score in each of the next four matches to become just the sixth player to score in five consecutive Champions League matches – something that even Messi has failed to do.
His eight goals in six matches, scoring on average every 47 minutes, is bettered only by Bayern Munich’s Robert Lewandowski as we arrive at the knockout stages.
The Norwegian will quickly get used to battling with Lewandowski in the scoring charts after his January switch to Dortmund and has taken the step up from RB Salzburg in his stride - to put it mildly.
Haaland scored what is fast becoming a trademark hat-trick on his debut, coming on as a 56th-minute substitute against Augsburg and putting the Bavarian side to the sword in the space of just 23 minutes.
A week later, again coming on as a second-half replacement, he scored twice against FC Koln as he became the first Bundesliga player to score five goals in his opening two games, achieving the feat in just 56 minutes of action.
He left Salzburg having netted 29 goals and notched seven assists in just 27 games and is already scoring more than a goal a game at Dortmund as he begins to post the sort of astronomical numbers Messi and Ronaldo take for granted.
So what of Mbappe?
Since bursting on to the scene with Monaco as a 16-year-old in 2015, his rise has been meteoric and well documented; he is already widely regarded as one of the best players in the world despite his tender years.
He also has a greater back catalogue of work than Haaland at the elite level, with this his fourth year in Champions League and Ligue 1 action, as well as having 34 international caps to his name.
In that time he has picked up a coveted Golden Boy award, handed out to the best under-21 player plying his trade in Europe – one of the few awards Ronaldo has missed out on. And Mbappe has already finished fourth in the Ballon d'Or rankings during his 2018 World Cup-winning year.
That’s not to mention being named in a Champions League Team of the Season, twice voted French Player of the Year, best young player at the 2018 World Cup and finishing as the Ligue 1 top scorer last season – as well as his numerous winners' medals, of course.
And if there were still any doubts about his potential, the fact his move to PSG made him the second-most expensive player of all time proves he is being tipped to go right to the top of the game. Not that he’s too far from it at already.
For the sake of argument, let’s take his Champions League statistics as a barometer of his development. This season, only the aforementioned Lewandowski (10) and Haaland (nine) have as many goal involvements (goals and assists) as Mbappe – five scored and four more created.
That equals his joint-best season, having scored four and created five in 2018/19, but he has done it in far fewer games having only been involved five times during the group stage (he missed the matchday one victory over Real Madrid because of a hamstring injury).
This season’s average of a goal every 66 minutes is by far the best it has ever been, surpassing his breakthrough year with Monaco, when he netted every 89 minutes. And his minutes-per-goal-involvement is at a remarkably low 37, more than half his previous best of 78 minutes, which he recorded last season.
During his first two full seasons he almost averaged a goal or assist every game he played at club level, which in itself is remarkable.
Yet last season he went to another level as he netted 39 goals in 43 club games in all competitions. And when assists are added in, that total becomes 56 goal involvements in 43 games – something close to the Messi and Ronaldo standard.
There’s been no let up this time around, either, with his strike rate at almost a goal a game in 2019/20 and his goal involvement numbers well above that.
At just 21, he is beginning to reach the unthinkable numbers the two icons of the sport have made their bread and butter.
There's another compelling reason to suggest Haaland and Mbappe could end up in the Messi and Ronaldo statistical ballpark by the end of their own careers.
Both are achieving their statistics impressively early in their careers, at ages where they arguably should still be learning the ropes at the top level.
While speculation over likely successors to Messi and Ronaldo can sometimes verge on the hyperbolic, what makes the case different with these two is that they’re making huge strides towards achieving the levels needed well before either the Barcelona or Juventus man were.
Before turning 20, Messi had made 12 Champions League appearances with just two goals and one assist to his name. Ronaldo, meanwhile, made ten, registering just one assist. Haaland, at 19, has eight goals and one assist in his six games so far.
Equally, before Messi’s 22nd birthday, his record had climbed rapidly with 17 goals and seven assists in 33 games, but Ronaldo was still to open his account, with just four assists in 23 appearances.
As for Mbappe, who turned 21 in December, he already has 19 goals and 12 assists in 30 games.
Of course, it remains to be seen if either Haaland or Mbappe can maintain these levels year after year.
But one thing is for sure: they're already giving themselves a fighting chance to claim the throne when the time comes.
Now, they come face to face for the first time on club football's grandest stage - and you'd be mad to miss it.
Tune in to BT Sport 3 HD from 7.15pm on Tuesday 18 February to watch Dortmund take on PSG in the Champions League last 16.