The Ligue 1 outfit lost the first leg of the quarter-final tie to a late Leonardo Bonucci goal, and their coach believes that only a "miracle" will see them progress.
"We are disappointed, but we knew before the game that Juventus are one of the best teams in Europe, so it was a mountain to climb," Garde told beIN Sports. "Now I think we need a miracle to score two goals in the second leg.
"We had the best scoring opportunities of the first half, but it is difficult to succeed at this level if you do not take your chances. It has been a great experience for my young players; like playing 100 games in one."
The return leg takes place in Turin next week.