Deschamps was in the stands on Friday as Inter slumped to a 3-0 home defeat to Bologna, their third consecutive Serie A defeat and second straight at home following the stunning 1-0 loss to relegation-threatened Novara.
That form has seen Inter drop to seventh in the table, heaping pressure on coach Claudio Ranieri, for whom the Champions League offers one final chance of redemption this season.
However, Deschamps is expecting to see a much stronger version of Inter tomorrow night.
"They are a team that is not playing well at the moment," he said in L'Equipe. "I have seen their previous matches on television, and there have been lots of individual defensive mistakes.
"But I am convinced we will not see the same Inter as of their last four Serie A matches. They will not erase everything in four or five days, but collectively they will be better.
"The Champions League can bring the focus and determination they have missed."
Marseille have been in less than convincing league form themselves, drawing their last two matches to fall further off the pace at the top of Ligue 1, with the gap to the top now 12 points, just two points better than the difference between Inter and Serie A leaders AC Milan.
Deschamps is now waiting to see whether this weekend's 1-1 draw with Valenciennes also cost him the services of Alou Diarra, who only resumed training today after suffering a toe injury and remains doubtful.
Inter will be strengthened by the return of Diego Milito and Dejan Stankovic, who missed the Bologna defeat.
Diego Forlan could find his place under threat with the return of Milito, but the veteran Uruguayan, who joined Inter from Atletico Madrid in the summer, still believes he made the right move and has backed Ranieri to turn the team's fortunes around.
"I came here, played a few matches, and then the coach changed. It happens - suffering an injury, too," Forlan told UEFA.com. "However I have always felt happy here; I'm totally convinced by the decision to come.
"Ranieri is a great coach. In fact I've played against his teams in England and in Spain a few times, and I always respected him. He's coached many big teams. Now I am coached by him, and it's a real privilege.
"We are convinced that we can return to how we were doing during that series of seven consecutive [league] wins."
