It is worth wondering 'What if?' What if Angel di Maria's time at Manchester United had coincided with a different manager to Louis van Gaal? What if he had persevered and waited for the coming of Jose Mourinho?
Di Maria suffered under Van Gaal. But he was not the only one. At various times during the Dutchman's reign, Wayne Rooney, Juan Mata, Ander Herrera, Robin van Persie, Danny Welbeck, Javier Hernandez and Radamel Falcao struggled for form or consistency.
In some of those cases, there were reasons at play beyond Van Gaal's tactical straitjacket. At some point, however, there needs to be a moment of reckoning, where it appears so many forward-thinking players were stifled that there must be a common denominator.
Angel di Maria scored twice as Paris Saint-Germain humbled Barcelona at the Parc des Princes
Di Maria gave the hosts the lead as his free-kick went through the wall on Tuesday night
DI MARIA'S CAREER 2005–2007: Rosario Central 2007–2010: Benfica 2010–2014: Real Madrid 2014–2015: Manchester United 2015– Paris Saint-Germain INTERNATIONAL 2008– Argentina Caps: 82 Goals: 18
From those who survived into the Mourinho era, improvement is clear in Herrera and Mata. Mourinho previously signed Di Maria for Real Madrid in 2010.
President Florentino Perez had fears that the Argentine winger would be unable to reproduce the form he had shown for Benfica but Mourinho insisted.
His faith was justified, to the extent that Cristiano Ronaldo was furious when Madrid sold Di Maria to United in 2014.
After Tuesday night's stunning performance against Barcelona, it's peculiar to think now of Di Maria's startling decline under Van Gaal. Mourinho did ask Di Maria to make sacrifices, dropping from the right flank to form a midfield three when Madrid defended and even playing at left back on occasion.
Other issues did not help. A hamstring injury curtailed a bright start and an attempted burglary at his home startled his family to the extent United placed a security guard to protect the Di Maria clan.
Yet United's players were disappointed by Di Maria's resilience. After six months, it seemed as though he had given up on a successful Old Trafford career. By the end of the campaign, he'd lost his place to Ashley Young.
Di Maria celebrates with team-mates Marco Verratti (left) and Julian Draxler after scoring
His second goal arrived 10 minutes after interval, as Di Maria scored from outside the area
DI MARIA 16-17 STATS Appearances: 26 Minutes played: 1856 Goals: 6 Shots: 79 Assists: 7 Chances created: 68 Ligue 1 and Champions League only
Not everyone in Manchester had been convinced about Di Maria's merits. Manchester City twice turned down the chance to sign Angel Di Maria in 2014, including in the same month as he joined United in a club record at the time £60m deal.
Di Maria had been offered to United's rivals in the two previous transfer windows. Arsenal also considered Di Maria before signing Mesut Ozil one year earlier.
Since leaving United behind and joining Paris Saint-Germain, Di Maria has been afforded more freedom by Laurent Blanc and Unai Emery. He scored 14 goals last season and the two wonderful goals against Barcelona on Tuesday night brought the tally for this campaign to eight.
In the French capital, Di Maria continues to divide opinion. Former France striker David Trezeguet criticised the winger just before the turn of the year.
The 29-year-old arrived at Manchester United in 2014 when Louis van Gaal signed him
Di Maria endured a frustrating debut season at Old Trafford and left the club for PSG in 2015
Manchester United fans will sympathise with Trezeguet's frustration. 'When he loses one or two balls at the the start of a game, it seems as though he goes missing or hides. He's got to force himself into it.'
It has been steady, rather than spectacular progress. Under Emery this season, there have been moments of difficulty and the arrival of Julian Draxler offered renewed competition.
'It didn't start off too well,' Di Maria told Spanish newspaper Marca. 'Those who know me know that I like to run with the ball and go a bit everywhere but he wants every player to occupy their space and press from their position. I found it difficult at the start but now I understand.'
In January, there were tenative approaches from China. 'Everyone thinks differently. It's not for me. I want to stay here and be happy. I came to Paris to win the Champions League.'
Perhaps now, his time has come.