Ranieri's side have made an instant impact on their return to the French top flight, amassing 18 points from their first eight league games in an unbeaten start to the campaign.
Ahead of tomorrow's clash with Saint-Etienne, the Italian has warned his star-studded squad that only a complete performance in all areas will be good enough to keep pace with Paris-Saint Germain.
He told reporters at a pre-match press conference: "This St Etienne side play good football and have very technical players. We will have to stay very organised and compact.
"St Etienne are a direct rival for us. I think they will be fighting for the leading positions right to the end of the season.
"We need to find the balance between defence and attack and that means total concentration for the full 90 minutes."