Chelsea will tackle Pep Guardiola’s side in an away Premier League tie at Etihad Stadium on Saturday afternoon.
Tuchel’s side are currently 10 points behind leaders Man City on the Premier League table.
However, Lukaku looks set to start for Chelsea after coming back into Tuchel’s squad following the controversy over an interview he gave to Sky Sports Italia.
But Williams wants Tuchel to feature Kai Havertz ahead of the Belgium international for this weekend’s Premier League tie.
“I think Kai Havertz could be a better shout against Man City than Lukaku,” Williams told Premier League Productions.
“It is hard to say that because look, if you were to ask me earlier on in the season who to start when Lukaku was in form and scoring goals, it would be easy.
“So of course, it would be a big decision but Lukaku looks like a player lacking confidence. He looks like a player who is desperate to show he wants to be there.
“He was so desperate against Tottenham to show Chelsea fans that he wanted to be there but in that desperation, you don’t perform. When you put too much expectation on yourself it can be hard to deliver.
“He was working hard off the ball which we haven’t seen often but that is not his game.
“Whilst he’s in that frame of mind where he is trying to prove to the fans, his teammates and the board that he does want to stay and that the interview was a mistake, it might be better not to play.
“I feel like he is not at the levels that Havertz is at right now and Chelsea need everyone at their best to beat Man City.”