Juve saw their 2-0 lead overhauled by the visitors to eventually lose 3-2 at home.
"We need to work harder and immediately put this defeat behind us," said the French hitman. "We must focus on the next game on Tuesday against Maccabi Haifa. That tie is all that matters now."
Juve were already four points off Serie A leaders Inter and could fall further behind after this weekend, while even second place is at risk.
"It was an excellent performance up until we were 2-0 up, then we all saw what happened.
"I know this is a painful moment, but we must think positive and above all stay calm. Tuesday's game is too important for us."