The England pair only recently joined up with the squad following their heroics at the World Cup, and the Foxes boss says the players need more time to recover from their busy summer.
"If we are serious I think they cannot participate in the first game, with just five days training with the team," Puel told the Leicester Mercury.
"They normally need more time, but we will see together with calm. We try to give good game time to work with the team and to make progress with their fitness, and it is important to respect this and to prevent injury."
The Frenchman continued: "We don’t rush these players. It is important after the World Cup to work but also come back with the team and live with the team to find again the atmosphere of the club and the squad.
"The players before worked a lot also. Of course Jamie and Harry are valuable players for us but we need to protect them. If they are available to play in their minds it is a good thing because this shows their desire to come back and fight with the team, but we have to take a protective decision from us."
Maguire has been the subject of intense transfer speculation and has been linked with a move to United. However, Puel has warned the club that selling the 25-year-old could have dire consequences for Leicester this season.
Puel told Sky Sports: "It's our intent to keep him and just a few days before the start of the season it would not be a good thing for the squad, for confidence and for Leicester.
"There is a possibility with the squad this season to do well and to continue to make progress, If we keep our best players we can do something interesting. We lost Riyad Mahrez and we know the importance of this player but we cannot lose another important player for this team."