Kevin de Bruyne and Romelu Lukaku had the shared experience of needing to escape Chelsea to realise the potential they displayed during their formative years at Stamford Bridge.
De Bruyne ended up at Manchester City via Wolfsburg, while Lukaku's more nomadic route took him to West Bromwich Albion, Everton, Manchester United then Inter Milan before he arrived back at Chelsea last summer.
Lukaku, who cost a club record £97.5m, always seemed destined to return to Chelsea at some stage, whereas De Bruyne - along with Liverpool's Mohamed Salah, also on the books at Stamford Bridge - must always be regarded as one that got away.
The London side were certainly happy to get their hands on Lukaku again. They would have been even happier to get De Bruyne back, and their respective contributions to Manchester City's 1-0 win at Etihad Stadium demonstrated exactly why this will always remain a pipe dream.
It was De Bruyne who demonstrated his world-class talent with 20 minutes left, curling a low right-foot finish past Chelsea keeper Kepa Arrizabalaga to settle this battle between first and second in the Premier League and extend City's lead to a seemingly unassailable 13 points.
He is one of the jewels in City's crown, the Belgian's languid style suddenly interrupted by flashes of pace, power and the deadly accuracy that finished off Chelsea here.
His compatriot Lukaku, in contrast, looks like a striker struggling for form and confidence, his current status not helped by an outspoken recent interview revealing discontent about his role that saw him dropped for the key game with Liverpool at Stamford Bridge and having to subsequently apologise.Manchester City 1-0 Chelsea: Visitors 'lacked quality' up front says Thomas Tuchel
Of more immediate concern to Chelsea and manager Thomas Tuchel was a laboured performance here in which he had two of his team's best opportunities but failed to profit from either of them.
In the first half, he broke into a good position but chose to pass on responsibility to the offside Hakim Ziyech when he should have taken on the chance himself. It smacked of a player short of conviction.
Even more costly was his failure to beat Ederson when clean through in the second half with the score 0-0, a finish slightly lacking in conviction offering the Brazilian the chance to make a fine stop.
'Sometimes he has to do the service'
Lukaku worked hard enough but those are the moments for which Chelsea parted with that massive fee. He was meant to be the striker adding the finishing touches to the chances they create - and he missed out here, that second miss proving so expensive in light of De Bruyne's winner.
"Sometimes he has to do the service," said Tuchel. "He had many ball losses and huge chance. Of course we want to serve him but he's part of the team. The performance up front in the first half, we can do much, much better."
Chelsea's manager sounded like he was trying to be sympathetic - but he also sounded like someone yet to be convinced by the qualities Lukaku can bring to his driven pursuit of the big prizes.
He was unhappy with Chelsea's attacking display in the wider context, saying: "The performance in the first half, in the opponents' half, we had eight or nine transition chances and out of them we didn't have a touch in the box.
"That you miss chances, I don't have a problem with that and of course you don't get a lot in top games. We could have had much more chances. The ball losses were too early and too poor. The decision-making was not on the level we need."
Lukaku has been finding the target for Chelsea when he has played but this will be another one of those occasions when his contribution against the bigger sides will be questioned - and there will be many more games like this as Tuchel tries to retain the Champions League as well as win the FA Cup and Carabao Cup.Man City 1-0 Chelsea: Guardiola praises 'well deserved' win over Chelsea
'The goal is typical of him'
Guardiola, in sharp contrast, was full of praise for De Bruyne. And rightly so.
"He's incredibly humble," said the Spaniard. "He always does it for the team. It's so difficult to find a player with this humility.
"I know the beginning of the season was not his best but we are always there to help him. The goal is typical of him. I'm very pleased for him because he deserved it.
"We have won what we have won together and now I want to push him more. He is a world-class player. He has won three Premier Leagues and a lot of prizes but I want more because I know he can do it.
"He has everything. He missed a bit of confidence this season. He struggled a bit but he knows what he can do. His mum and dad have to be so proud of him."
Those contrasting messages from the two managers said it all on a day when De Bruyne created and finished City's big moment and Lukaku missed his.Our coverage of your Premier League club is bigger and better than ever before - here's everything you need to know to make sure you never miss a moment