The French club's all-time leading scorer is out of contract at the end of the season and has cut a frustrated figure since returning from a hip injury last month.
He was an unused sub in the wins over Nice and Club Brugge last month and has been restricted to appearances off the bench in PSG's three most recent matches.
However, in-form striker Mauro Icardi is a fitness doubt with a foot injury sustained in Wednesday's 1-0 win against Club Brugge, opening the door for Cavani to make his first start since August 25.
"It is complicated for him because he's used to starting every game," Tuchel said at Friday's pre-match news conference.
"For the last few weeks, it has been a big difference for him in terms of pace and speed. He has trained well and it is important he starts and regains his rhythm.
"He is disappointed not to play but accepts the decision and has kept a good state of mind."
Cavani has finished as Ligue 1 top scorer in two of the past three seasons and scored twice in as many matches prior to picking up his injury against Toulouse.
PSG boss Tuchel is hopeful that this weekend's clash will give the Uruguay international an opportunity to revive his campaign.
"I'm hoping that playing on Saturday will be a trigger for him," he said. "I do not like having Edinson on the bench, but I have made that decision.
"He is an important player for us and I want him to start tomorrow. If he can score that would be good news for PSG."
PSG suffered a shock 2-1 defeat at Dijon last week - their third loss of the campaign - and Tuchel suggested motivation may be an issue against lesser opposition.
"We can lose, it happens, but it must only happen against better sides than us," he said. "If we are missing key players, that matters - like [Marco] Verratti against Dijon.
"We do not always perform at the same level. That doesn't mean the match isn't important.
"We have to accept that the tension is different before Champions League games, or the Marseille match, compared to when we faced Dijon.
"We have to respect the opposition and prepare ourselves in the same way. I have players who know that and are super reliable."