Tiemoue Bakayoko. If Chelsea fumble this one, there'll be nowhere to hide.

As much as Romelu Lukaku, now of course of Manchester United, had an emotional attachment to Chelsea, the Blue ties for AS Monaco's powerhouse also run deep. For without the intervention of Claude Makelele, Bakayoko may never have survived his first two years at ASM.

It was the former Chelsea midfielder, now an assistant coach at Swansea City, who gave a nonchalant Bakayoko a heavy dose of 'tough love' after the midfielder's difficult first months with ASM.

The all-action midfielder that we see now. The inspirational, box-to-box dynamo we've celebrated this past season. It wasn't always like that. Indeed, for the first two seasons at ASM, the €8 million paid to Rennes looked a very expensive mistake.

The Parisian was blowing it. Hooked just a half-hour into his debut, Bakayoko appeared destined to never recover. Leonardo Jardim, the Monaco coach, had quickly given up. He tried the arm around the shoulder. Then the hairdryer. But nothing worked.

"I expect players to work to progress and so they can aspire to bigger teams. He's had difficulties. And so, he can not always play. It's complicated when there are more coachable players in the same position," stung Jardim.

Bakayoko, having failed so miserably to offer an alternative to then captain Jeremy Toulalan, soon disappeared from view. The midfielder struggled to even make Jardim's bench. And when, at the end of that first season, he went seeking an explanation from the manager, the feedback was anything but positive.

Indeed, the following season, Bakayoko's prospects worsened. Jardim welcomed Mario Pasalic on-loan from Chelsea, yes that lot again, and immediately installed the Croatian ahead of Bakayoko in his midfield pecking order.

Pasalic's form and a thigh injury relegated Bakayoko to the stands for the first-half of the 2015/16 season. But it was while in traction that the rebuild began. First it was the intervention of Makelele, then ASM's sports director.

The World Cup winner didn't hold back. Bakayoko's attitude. His work ethic. His lifestyle. The lack of respect for his profession. It was all examined. Makelele also had Yannick Menu, Bakayoko's former junior coach at Rennes, join him in pulling apart Bakayoko. It was make or break time for the midfielder. And, thankfully for him, Bakayoko was receptive.

Indeed, so much so, that everything changed. A villa boasting an inground swimming pool was dumped for an apartment. A pink porsche swapped for matt black. A fulltime fitness trainer was hired. As was a dietician. By the end of that season, Bakayoko's body had transformed. As had his mind - thanks to Makelele.

There was no arm around the shoulder from Makelele. He prodded Bakayoko. Poked him. Wound him up. The mental fragility which had so disappointed Jardim had gone - and the coach was impressed.

"Last year, there was Jérémy Toulalan in his position. With his departure, he gained confidence. But it's also more about the time Bakayoko has been here and working with us. He's growing up," said Jardim.

And that's where Bakayoko stands today. A year on from Jardim's hard won praise and he is now among the most coveted - and feared - midfielders in Europe. Only Real Madrid's Champions League winner Casemiro won more tackles in the competition last season. Those changes have clearly worked.

"I have a personal physical trainer, a mental trainer, an osteopath. In my approach to football, I try to be as precise as possible in relation to my body," Bakayoko says.

"In Paris, it forged my character. I had to fight.

"As a kid, I wanted to play in big games. And thank God, I realized this dream. But that's not enough. I am very ambitious..."

A theme through Bakayoko's career has been fighting back. As much as the Jardim bust-up rattled him - and by his own admission it did - he was prepared. As a junior, Bakayoko was rejected by the famous Clairefontaine academy, though it had nothing to do with his footballing ability. Instead, a poor school report saw him turned down.

"It hurt at the time, but going to Clairefontaine may've stalled my development. Out of bad, you can find good."

It's that strength of character which now has Chelsea and Manchester United fighting over his signature. The latest out of France is that Chelsea have stepped back, with Bakayoko requiring clean up surgery on a troublesome knee strain. However, Jose Mourinho and United have no such issues and are even willing to meet ASM's €40 million asking price.

Whatever develops over the coming days and weeks, Bakayoko is sure to take it all in his stride. The attitude has been adjusted. The pink porsche scrapped. Whichever club wins Bakayoko's signature will be getting a far better professional than the one who walked into the Stade Louis II three years ago.

"I have not changed. My parents gave me a good education. I'm a soccer player, I kick a ball ... There are more important things in life - like building a family."