Saint-Andre, with his staff, watched France's 30-12 victory over Italy in their Six Nations opener twice overnight and could see the World Cup runners up struggled to put pressure on their opponents in the rucks.
"We lack that ferocity, that desire to go forward," Saint-Andre told reporters on Sunday, although he praised his players for their capacity to follow orders.
"We were more in a training session than in an official match," he said.
"When we upped the pace, we were better in attack and in defence.
"We cannot let the Irish play like they want because they will score when they have the opportunity. We will have to take them by the throat."
Saint-Andre, who took over from Marc Lievremont last December, said there would be changes to the starting line up for the match at the Stade de France but thought there was much to build on.
"I'm not depressed. We won. We scored four halfback tries," he said.
"We were not dominated, we defended very well, we were disciplined. There is a lot to take into the next games."
The great defence, "Lievremont's legacy", according to Saint-Andre, is something to build on but it will not be enough against Ireland.
"We must be more precise. Our defence is very well organised but we lacked aggressiveness," the former France wing said.
"We should have deprived them of space. We lacked consistency in terms of gaining possession and we need to improve our lineouts, which were not great at all."
Saint-Andre will name his team on Tuesday.
Forwards: David Attoub, Vincent Debaty, Nicolas Mas, Jean-Baptiste Poux, William Servat, Dimitri Szarzewski, Pascal Pape, Yoann Maestri, Lionel Nallet, Julien Bonnaire, Thierry Dusautoir (captain), Louis Picamoles, Imanol Harinordoquy.