The French boss revealed he turned down the opportunity to sell the highly-rated midfielder to Nice last summer, while hinting at the arrival of more players this month
The Stade Gerland outfit carried out major modifications to the squad after a underwhelming 2011-12 season which saw the club finish fourth, but Garde maintains Grenier's status within the side was never in question.
"Grenier is a player for the future of this club," revealed the 46-year-old to L'Equipe. "I was adamant in my decision not to allow him to depart for Nice last summer.
"I think he showed in the matches before his injury that I was not wrong. We are now trying to work out a suitable contractual extension that would satisfy all parties."
Les Gones now sit joint-top of Ligue 1 alongside Paris Saint-Germain and Marseille, and Garde has declared the club will continue strengthening their ranks during the weeks ahead.
He added: "The market is very quiet today, but anything and all can happen before it closes. For that reason, we will keep an eye open till January 31.
"There is no question of selling any players, as all within this team represent their personal value within my plans."