Michael Jackson has had so many cosmetic surgeries that he might face difficulty opening his mouth wide enough to hit the high notes when he kicks off his London comeback tour.
And producers fear that the erstwhile King of Pop might have to compromise on his voice while belting out hits, because of his multiple surgeries.
The London shows also face a recording ban, and thus concertgoers cannot analyse the sound too closely.
And videos of his hits could be played during the show to cover the star as he performs.
The 50-year-old singer will also be protected by an army of dancers and stage pyrotechnics at the sell-out gigs at the O2 Arena.
"An issue has arisen as a result of the medical work Michael has had," the Daily Star quoted a top music promoter as saying.
The promoter added: "Just making the right sounds is tough due to the surgical work. He doesn't want to disappoint fans with a second-rate performance and steps are being taken to ensure he has some back-up."