The French coach has also called on his players to unite in an effort to kick-start their campaign.
Five matches into the new Ligue 1 season, Marseille - champions just two seasons ago and runners-up last term - remain winless with a record of three draws and two defeats, the latest a 1-0 reverse to Rennes that has left the Mediterranean club just above the drop zone.
OM's poor start means they have now gone eight Ligue 1 games without a win dating back to the end of last season - their worst ever run under Deschamps.
The loss to Rennes again highlighted the extent to which confidence has drained from the team, and Deschamps admits there were worrying signs on display at the weekend.
"When they scored, we looked fragile," said Deschamps.
"Of course, it's hardly ideal in terms of confidence ahead of the Champions League. We have to get over our disappointment to be ready for the best competition in Europe.
"We have to show solidarity and determination to turn things round."
A win in their Group F curtain-raiser in Greece on Tuesday night would be as good a place as any to begin their revival, particularly as their hosts have yet to kick a ball in anger this season.
Olympiacos' first two Super League matches were postponed after their scheduled opponents, Kavala and Olympiacos Volou, were relegated to the fourth tier owing to match-fixing offences.
The reigning Greek champions' last competitive outing came against Larissa in April, and Ernesto Valverde's ring-rusty troops could be the perfect opposition for a Marseille side desperate for a win.
Yet even if the home players are below their best, Olympiacos' passionate home support at the Karaiskakis Stadium will doubtless be on hand to give the visitor their customary hostile welcome - although OM midfielder Benoit Cheyrou insists he and his team-mates will not be fazed by the hot reception.
"We know what to expect there but for a player it is more motivating to play even in hostile environments," he said.
"It does not bother me and no one is afraid to play there."
Injuries could yet scupper French hopes, however, with Stephane Mbia out with a broken metatarsal and doubts over the fitness of influential duo Mathieu Valbuena (knee) and Andre Ayew (groin).
For the hosts, Ariel Ibagaza is out after knee surgery, although Avraam Papadopoulos, Francisco Yeste, Olof Mellberg and Rafik Djebbour are expected to shake off knocks in time to feature.