Kevin De Bruyne approaching Keane, Vieira, Gerrard levels at Man City
There must be times when Jose Mourinho feels like the record label executive who turned down the Beatles when he sees Kevin De Bruyne inspiring Manchester City to yet another emphatic victory.
Only Mourinho truly knows why he allowed De Bruyne to grow so frustrated with his lack of opportunities under the Portuguese coach at Chelsea that he forced a move away from Stamford Bridge in January 2014, just six months after Mourinho had taken charge at the club.
De Bruyne's loss was not instantly felt by Mourinho and Chelsea, who won the Premier League title in 2014-15 while the Belgian midfielder was quietly proving his old manager wrong at Wolfsburg.
But almost four years after Mourinho and De Bruyne parted ways, it now seems inconceivable that a player of such quality was allowed to slip through the net by such a high-profile manager and a club as powerful as Chelsea.
At 26, De Bruyne has become one of the most influential midfielders in Europe with City and in Pep Guardiola's all-star team, he is arguably the one player at the Etihad who is irreplaceable.
Saturday's stunning goal in the 2-0 win against Leicester City was De Bruyne's third of the season in the Premier League -- he also has six assists -- and few would bet against him hitting double figures for the first time in the league this term.
But it is more than the goals and assists which have made De Bruyne so important to City. His development under Guardiola into a midfield powerhouse capable of scoring, creating and dominating his opponent makes him perhaps the greatest example of the manager's methods bearing fruit at the Etihad.
Leroy Sane has made huge strides under Guardiola. Raheem Sterling is now smoothing off his rough edges and John Stones is becoming the confident ball-playing centre-half that many expected him to grow into, but nobody has quite kicked on as much as De Bruyne under Guardiola.
Since the Premier League began in 1992-93, three midfielders have gone on to become the dominant figures of their generation -- players who have led for others to follow.
Roy Keane, Patrick Vieira and Steven Gerrard continue to be held aloft as the standard and De Bruyne is now on course to become their natural successor as this era's leading midfielder.
Some will argue that Frank Lampard should also be on that list, and the former Chelsea midfielder certainly scored the goals to earn comparison with the best, but Keane, Vieira and Gerrard lifted their teams and teammates to greater achievements and De Bruyne now has the opportunity to do the same at City.
Mark Hughes, the Stoke City manager, described De Bruyne as "world-class -- head and shoulders above everyone else in the Premier League," after watching the player pull the strings in a 7-2 win against Hughes's team. De Bruyne created five goals for City that day, with one majestic pass leading to a goal for Sterling that has already become one of the moments of the season.
Keane, Vieira and Gerrard possessed different qualities which made them so important to their respective teams. Keane's leadership and ability to control the tempo of a game gave Manchester United the rock around which Paul Scholes, David Beckham and Ryan Giggs could produce their creativity, while Vieira's power, energy and sheer force of his presence made him the kingpin of Arsene Wenger's great teams at Arsenal.
And Gerrard, while he did not win a Premier League title during almost two decades at the heart of Liverpool's midfield, often dragged the club to success in the biggest games and occasions, with his match-winning contributions in the 2005 Champions League final and FA Cup win against West Ham the following year defining his Anfield career.
All three players projected an air of invincibility when at their best and De Bruyne is developing the same aura with City.
When opponents line up against City in the tunnel, the sight of De Bruyne will lead to thoughts of just how he can be stopped. How can his defence-splitting passes be nullified, who can match his box-to-box energy, is there a way to prevent him scoring if he has a sight on goal from 20 yards?
De Bruyne is surrounded by great players at City, with David Silva, Fernandinho, Sane, Sterling, Gabriel Jesus and Sergio Aguero all capable of making his good work pay off.
But he is the cog around which City are turning right now and, at 26, he is approaching the prime of his career.
He must still win trophies in England and Europe before he can truly join Keane, Vieira and Gerrard in the pantheon of the Premier League's greatest midfielders, but he is getting there.
And the fact that he on course to do so after being rejected by Mourinho and Chelsea will make it even more satisfying for De Bruyne when he achieves it.
Mark Ogden is a senior football writer for ESPN FC. Follow him @MarkOgden_