Ousmane Dembele has long had a big reputation.

The forward - who was once the second-most expensive player in history when he signed for Barcelona from Borussia Dortmund in 2017 in a deal worth £135.5m - was described by Barca president Joan Laporta as "better than Kylian Mbappe" in 2021.

A week later, then-new Barcelona manager Xavi Hernandez said he was a player who, "when used properly, could be the best player in the world".

Two months on, having been told by a cash-strapped Barcelona to accept a new contract on reduced terms or leave, Xavi dropped him from the squad.

That story reflects his time at Barcelona, a six-year spell of inconsistency and unfulfilled potential.

In August 2023, the France international was bought by Paris St-Germain for just £43.5m, having scored 40 goals in 185 games and won three La Liga titles.

Now - with 10 goals in his past five games - he is currently Europe's most in-form striker, drawing comparison to the likes of Lionel Messi, who scored 13 goals in four games in March 2012, and Cristiano Ronaldo, who hit 11 goals in four games in May 2011.

He is also being seen as PSG's trump card in their quest for a first Champions League trophy.

The 27-year-old has scored 18 goals in his past 11 appearances for PSG in all competitions and since the start of December, has scored more goals (18) than any other player in the big five European leagues.

So, as PSG go into Wednesday's Champions League play-off second leg against Brest with a 3-0 lead, what has changed and can his remarkable form last?

Dembele arrived at Barcelona aged 20 as their most expensive signing, but his time at the club was a mix of injury setbacks and off-field issues.

Despite being largely injury-free at Rennes and Dortmund, he sustained 14 muscle injuries at the Nou Camp, spending 784 days sidelined.

Concerns over discipline and professionalism led the club to assign private chefs to him, while late nights because of gaming affected his training punctuality, making him the club's most-fined player in recent years.

Still, when fit, his explosive pace and dribbling made him a game-changer, as he showed glimpses of the talent Barcelona invested in.

So what changed him?

Those that know him best - and few do - say he changed after marrying his girlfriend Rima at a Muslim wedding in Morocco in December 2021, and soon after he had a child.

The wedding came as a surprise to many of his team-mates, not least because they did not even know he had a partner.

So the big changes to his life occurred in his last two seasons at Barcelona when, essentially, he grew up.

He worked at home with a physiotherapist and frequently went to France to receive specialised preventative treatments. With the eyes and mind of a father, he began to see things differently.

He finally took on board the importance of good nutrition and, for the past few seasons, has employed a French nutritionist who has helped him maintain a healthier lifestyle.

Dembele always enjoyed the respect and esteem of his Barca team-mates, many of whom were surprised and disappointed to see him sold to PSG.

Dembele has never lacked confidence, is super-passionate about football and arrived in Paris in August 2023 convinced of his ability to star and succeed at the club, despite the presence at the time of Mbappe.

Last summer, manager Luis Enrique told Dembele that, without Mbappe in the team, he needed more goals from him to go with his large number of assists - carte blanche for the player to show a more selfish approach with less passing and a bigger desire to score.

In private, the coaching staff have frequently told him that if he managed to convert a decent percentage of the chances that he creates, it can lead to collective success and then individual honours. The Ballon d'Or even.

He has taken it all on board and is relishing playing in his new tactical role.

Last season, he was mostly played on the right. Now he operates as a false nine, inside, where he touches the ball more, enjoys a greater freedom to receive passes and participate in the build-up but with more chances to finish.

He is enjoying talking about tactics, about how to improve and about understanding the game. He is now the complete opposite of how he was perceived by many at Barcelona.

And the goals have flowed. His tally of 23 coming from all angles.

This season, he has scored 16 in Ligue 1 (eight with his right foot, six with the left, two headers), six in the Champions League (four right, two left) and one left-footed goal in the Nations League.

It has not all been smooth sailing for Dembele in Paris though. Despite his quiet facade, he still has fire inside.

In September, following PSG's 3-1 victory over Rennes, there was a heated exchange between player and manager - leading to Dembele's exclusion from the squad for a subsequent Champions League match against Arsenal.

Luis Enrique emphasised the importance of players fulfilling their responsibilities to the team, saying: "When a player doesn't meet their obligations, this is the sort of thing that can happen.

"The best thing I did was not to play him in London against Arsenal, even though that was heavily criticised. This is my best decision of the year. He did the rest himself."

Dembele did not like the way he had been talked to by the manager in front of the squad and overreacted. Soon after he apologised.

He was also sent off against Bayern Munich and after that, spending two games on the bench, it was incorrectly suggested that Luis Enrique had punished him.

He was actually rested because the coach thought he was a bit unfocused and needed a mental rest. Those two games were two unexpected draws against Nantes and Auxerre.

This week we saw a video of training with the two men hugging and laughing.

Luis Enrique was also full of praise for Demble after he scored twice in the first-leg win against Brest.

"Ask him what he has had for breakfast since Christmas! Actually those who see him regularly are not surprised," he said.

For some time many have believed that the holy grail of a Champions League triumph for PSG might be dependent on the on-field achievements of one of France's heroes.

That could still be the case - just not with Mbappe, but a rejuvenated Dembele.