Chelsea fans did not 'really appreciate' Romelu Lukaku during his stint at Stamford Bridge, according to former left-back Ashley Cole.
Lukaku moved to the Blues from Belgian side Anderlecht a decade ago when he was just 18 years old in an initial £10million deal.
But the Belgium forward would only go on to make 15 senior appearances without scoring in west London, including a solitary start in the Premier League against Blackburn in May 2012.
It was a different story for Lukaku when he went out on loan to West Brom during the 2012-13 season and to Everton in the following campaign, netting 17 league goals for the Baggies and 15 for the Goodison Park outfit.
His form for the Toffees ensured he sealed a £28m move to Everton in 2014, which preceded a £75m transfer to Manchester United three years later and a £73m move to current club Inter Milan in 2019.
And speaking to ITV before Belgium's 2-1 win against Denmark in their second Euro 2020 match in Copenhagen on Thursday, Cole claimed the Belgian's rise from the player he shared a dressing room with has been 'exceptional'.
'At 17, I probably had a better touch than him but when he receives the ball it is completely different as he is constantly under pressure, but since it has improved massively and his link up play for club and country is exceptional,' Cole said.
'The two loans gave him that self-belief to really kick on because at Chelsea, he wasn't really appreciated by the fans, but he went out on loan to prove himself and now he is one of the best strikers in the world.'
Cole also explained his former team-mate and Blues legend Didier Drogba - who scored 164 goals for the club and won four Premier League titles and a Champions League crown - helped Lukaku to improve his game.
'Didier Drogba was like a father figure to him at Chelsea early in his career, and helped him develop his technique and improve as a striker.'
Lukaku has previously stated his admiration of Drogba, praising the ex-Ivory Coast striker and Nicolas Anelka for their impact on his career.
'I was only 18 years old, I had just finished high school three months earlier, I had graduated and suddenly I was already on the train to London,' he told Bleacher Report via Goal.
'There I met Didier Drogba, he was doing physiotherapy. He told me immediately that I had to show him the 'Blue' character.
'From that day on we started talking every day for at least an hour, before training, after training. He, Anelka and every other player in that locker room showed me what it takes to become the person I am today.
'It wasn't so much the coach as the players, they had a mentality that made them say ''OK, let's go win''.
'It was a great experience, I saw how they won the Champions League, the FA Cup and this has served me well so far.'