Giresse saw his men succumb to a 3-1 loss in Abidjan last month but remains confident in their ability to overturn the deficit when the two sides meet again for the second leg in Casablanca on Saturday.
Goals from Didier Drogba, Salomon Kalou and a Ludovic Sane own goal put Ivory Coast on the verge of a third consecutive finals appearance, but Papiss Cisse's late consolation has given Senegal a glimmer of hope.
"We have to believe," Giresse said. "It is very simple. We know what must be done and what remains to be done to qualify.
"We have to score two goals to qualify for the next World Cup. The challenge is there."
The fact that the match is being played in Morocco is likely to make Senegal's task even harder, with the change of venue introduced as punishment for the rioting that took place when the two went head-to-head last year in an African Cup of Nations qualifier.
Ivory Coast have only lost one competitive game in 2013 – against Nigeria in African Cup of Nations quarter-final – and went through their whole qualifying campaign unbeaten.
They will be without midfielders Cheick Tiote and Geoffroy Serey Die through suspension, while Boka Arthur (groin) and Siaka Tiene (hamstring) are both unavailable to coach Sabri Lamouchi.
Senegal have only lost one of their last six matches under Giresse, but since their stadium ban they have won just one game when they have been the nominated home team.
That victory, which came against Uganda in Marrakech, helped secure their place in the play-offs and kept alive their hopes of making a second World Cup finals in their history, and first since 2002.
Senegal have no new injury worries but will be without Demba Ba after he was left out by Giresse.
