Radja Nainggolan has claimed he warned Romelu Lukaku against returning to Chelsea last summer.
Lukaku rejoined Chelsea from Inter in a club-record £98 million ($126m) deal in August 2021, bringing to an end his impressive two-year stint in Serie A.
The Belgian striker fired Inter to their first Scudetto in 11 years last season, but has been far less prolific in his first year back at Stamford Bridge under Thomas Tuchel.
What has Nainggolan said about Lukaku?
Lukaku has lost his place in Chelsea's starting XI due to his poor form, and Royal Antwerp star Nainggolan believes he made a big mistake by deciding to leave San Siro.
The former Inter midfielder, who also previously played alongside Lukaku at international level, told Fanpage: “I had told Lukaku that he was the best striker in the world at Inter. The team and the tactical system were shaped around him.
"He dreamt of making it at Chelsea, but it’s the second time that he goes there and it always ends up in the same way.
“Had he stayed at Inter, he would have been the best striker in the world for four or five years and I keep telling him this."
Lukaku's underwhelming record at Chelsea
Lukaku failed to find the net in any of his 15 senior games for Chelsea between 2011 and 2014 before being sold to Everton.
The 28-year-old, who also had an unsuccessful spell at Manchester United before joining Inter in 2019, said he had unfinished business with the Blues upon his return to west London, but has only managed to score 12 goals in 38 appearances in 2021-22.