The Belgian striker scored 25 league goals for the Toffees last season, but has since expressed his desire to leave the club.
It was only two years ago when Lukaku was sold to Everton for a club record fee, however, reports have linked the 23-year old with a £100m transfer back to Stamford Bridge.
But Nicol believes Lukaku will struggle to fit Antonio Conte's system.
"He's going to a great team in Chelsea but I'm not sure he fits in," Nicol said on ESPN.
"This is definitely going to happen but my goodness, when you've got rid of a player and then you spend a crazy amount of money getting him back.
"If indeed it happens, every man and his dog say it's going to happen, I'm sure it will.
"Is he going to be a hit? I'm not so sure."