I was watching this fabulous program last night.
Back then I was a huge fan of Zizou and Djorkaeff especially, I didn't know that much about the younger players. So I don't recall much about Trez's role but I was reminded that he scored against Saudi, but then he also provided the assist for Blanc's all important extra time goal against Paraguay.
It's 2002 that really could have been glorious, Henry and Trez were starting together. Unfortunately, the muppet Lemerre was in charge. In 98 Lemerre was basically the fitness coach.

And while a fitness coach is crucial, that's not to say he's right for head coach. Jacquet was the one who did all the mental preparation, the motivational speeches, the tactical instructions. Since then of course the team has had a series of completely inept muppets, one worse than the next, up and including the dark ages of Domenech.
Incidentally, it's not that surprising that Deschamps turned out to be a great coach, because as captain in 98 he was already really involved in discussing how they should play, making little pep talks with certain players etc.