Roberto Mancini's side have been well off the pace in Serie A, have exited the Coppa Italia and are now out of Europe after a 5-2 aggregate defeat to Wolfsburg.
Thursday's 2-1 defeat at San Siro extended Inter's winless run to five games in all competitions, and Ranocchia knows things need to change in the final 11 games to avoid a disastrous campaign.
"We are disappointed because we really believed that we could qualify and had prepared well for this game," he told the club's official website.
"We had many chances but unfortunately we could not use them, unlike them.
"Now we must concentrate all our strength on the championship. We need to do something to cut the gap in the standings."
Inter's fans left their team in no doubt about their feelings after the Wolfsburg defeat, with those remaining in the stadium jeering the players off the pitch at full-time.
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