Inter snapped a three-match losing streak with a 3-0 victory over Palermo on Sunday, taking them up to 10th in the league – five points off a European place.
Roberto Mancini has struggled to revive Inter's fortunes since replacing Walter Mazzarri in November but, with fixtures against Atalanta, Cagliari and Fiorentina intertwining European meetings with Celtic, Hernanes is confident they can find form.
"I feel the confidence of Mancini," he said.
"The important thing is to move on as a team from this period in which we were not getting results.
"No matter who plays, whoever is on the field must do better. Now it's time to get down to work.
"This is the moment of truth and we can’t afford any more mistakes."
Inter host Celtic in two weeks' time in the first leg of their round-of-32 Europa League clash before heading to Glasgow.
Hernanes stopped short of labelling winning the competition as a defined ambition, but he believes the knockout format could play into their hands.
He added: "Europa League? This is not the time to set targets.
"But it is certainly a goal as it is only seven games [between now and winning the final]."
