Man Utd vs. Chelsea a reminder of what could have been for Luke Shaw

"If we pay to a 19-year-old boy what we were being asked for, to sign Luke Shaw, we are dead. We would have killed our stability with financial fair play and killed the stability in our dressing room."

That was Jose Mourinho in July 2014. The Manchester United manager was producing memorable quotes about his left-back long before he reacted to the substitute's cameo against Everton last week by suggestion it was "my brain in his body." In 2014, Shaw was considered a prodigy: he was voted the best left-back in the Premier League by his peers, ended Ashley Cole's England career and appeared in a World Cup, all before his 19th birthday.

Then a decision beckoned: move to Stamford Bridge or Old Trafford? Shaw, a Chelsea fan with geographical reasons to make the short journey up the M3 from Southampton rather than a lengthier move up to Manchester, opted for the latter.

If Mourinho's 2014 analysis is correct, finances dictated his destination. Admittedly, he had less issue with a policy of blowing rival suitors out of the water with a huge offer when United used it to entice Paul Pogba two years later. But Shaw, who cost an initial £27 million, has gone from being the world's fourth-most expensive defender ever at the time to being United's fourth-choice left-back two weeks ago. He could spend Sunday facing the club he might have joined.

Considering that Shaw didn't appear in the Premier League between October and March, it would represent a revival in his fortunes. Mourinho has criticised Shaw for his positional sense, his poor performance in September's defeat at Watford and his efforts in training. While the Englishman has vowed to prove his manager wrong, one theory is that the Portuguese, who places great stock in loyalty, has never forgiven Shaw for rejecting his advances three years ago.

The defender's United career may suggest that Chelsea have few reasons to rue the one that got away. While Ryan Bertrand, Shaw's successor at Southampton, took his place in the following season's PFA Team of the Year, Cesar Azpilicueta went on to claim his unofficial status as the division's outstanding left-back. Now that mantle may rest with his Chelsea teammate, Marcos Alonso.

Azpilicueta had displaced Cole from the Chelsea side months before Mourinho bid for Shaw, and the Spain international's adaptability has been displayed again since Antonio Conte converted him to a right-sided centre-back. It was first evident under Mourinho, an antidote to the modern breed of managers who select full-backs primarily for their attacking qualities. Azpilicueta's positional discipline and defensive reliability made him the equivalent of William Gallas, another right-footer Mourinho used on the left at the expense of supposed specialists in a title-winning campaign.

Azpilicueta's almost three-year reign as first-choice left-back was only ended by the arrival of a compatriot and a piece of imaginative thinking by Conte. Alonso may lack the speed Shaw could bring, but he has offered an understanding of the wing-back's role, game intelligence and the ability to make telling contributions. His five goals have included a brace against Leicester, the opener against Arsenal and last week's fine free kick at Bournemouth. An unheralded arrival is shaping up as one of the signings of the season.

So Chelsea have been well-served on the left of their defence, but not by Shaw's immediate successors. Mourinho suggested that if Chelsea had acceded to Shaw's wage demands, more seasoned players would have demanded pay rises too. But another interpretation is that it was a false economy not to pay up.

There is no guarantee Shaw's career would have stalled at Stamford Bridge in the way it did at Old Trafford. Certainly he might not have suffered a horrific double leg break, from which he's arguably never fully recovered, and while Alonso could be deemed a case of third time lucky, he was the third left-back Chelsea signed in as many summers. Filipe Luis cost £15.8 million in 2014 and made nine league starts, Baba Rahman came for a fee rising to £22 million in 2015 and began just 11 top-flight games. Neither displaced Azpilicueta; neither is at the club. Luis was sold back to Atletico Madrid for a slight loss, and the latter is on loan at Schalke.

Including Alonso, Chelsea have committed £57 million to left-backs since Shaw snubbed them. That sum could rise again this summer. Because Alonso has made 25 consecutive league starts, Conte has not needed an alternative: there are also suggestions that Nathan Ake or Kenedy could understudy him, but each is better suited to other positions.

The logical assumption is that Azpilicueta is too important elsewhere to revisit his past. Because Chelsea have been virtually injury-free and out of Europe, it has not mattered, but there is a gap in the squad. Unless Rahman is recalled, Chelsea's annual, expensive pursuit of a left-back could continue at a time when it is hard to escape the sense that Mourinho's rapprochement with Shaw is only temporary and that he will leave Old Trafford.

Three years on, Shaw's move has not worked out the way either he or United envisaged. But while it is camouflaged by the current excellence of Azpilicueta and Alonso, perhaps Chelsea did not benefit either.