A double from Floyd Ayite gave Bastia a 2-0 victory in Saturday's round-of-64 match as Lille suffered their sixth loss in the past 11 games.
Lille had seemingly turned their form around before the French football season's Christmas break, winning consecutive games against Toulouse and Bordeaux, before just going down 2-1 to Ligue 1 leaders Marseille.
But Saturday's loss left Girard with more questions than answers as his team was eliminated from the Coupe de France in their first match in two weeks.
"In barely exaggerating, I think if we had not wanted us to qualify, we would not have done better," he said.
"There is not much to be learned from this meeting."
The 60-year-old added: "We are in a complicated period with several injured players and others who went to [the African Cup of Nations]."
Lille captain Rio Mavuba urged his team-mates to move on quickly from the loss in Corsica, as the northerners will host Evian and Caen in the league over the next week.
"We will have to take maximum points at home," the midfielder said.
"This can raise us in the league, and maybe start a run. That's our goal.
"But to hope to accomplish, we have to show another face than was glimpsed tonight.
"We know that to our audience, we are able to make beautiful things. We saw that against Toulouse."
Lille defeated Toulouse 3-0 in their penultimate league fixture before the Ligue 1 break.
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