Lukaku was announced by the Blues on Thursday, having joined from Inter Milan for a British record fee of £98 million.
The Belgium international is returning for a second stint with Chelsea after parting ways with them seven years ago.
The 28-year-old failed to impress during his first stint with the Blues and was shipped out on loan to West Bromwich Albion before eventually being sold to Everton in 2014.
Despite returning to the Stamford Bridge as a much more mature striker, Yahaya Mohammed is not enthused by the move.
“I really love him so much that they called me Lukaku too in Ghana. [But it] is a mistake for him to move back to where he did [not] make it before. I am really scared for him hmmmm,” the Ghanaian tweeted.
After being criticised by some Chelsea fans, he clarified: “I am not talking anyhow. You have to understand what I said. I never wished him bad.”
Meanwhile, Chelsea manager Thomas Tuchel believes Lukaku’s addition will help make his team better.
"We're happy to have Romelu back in the club; we think in terms of personality, speed, power, he can be hopefully an excellent choice for us," the German said.
"He has the power, the physique to help us, he has the experience, the personality to have a huge impact. He is at the same time a humble guy, and a true team player and he cares about Chelsea.
"We had the feeling that it's worth to try and fight hard and we are happy he is our player now,” he added.