Simone Inzaghi acknowledged Inter must show greater maturity in their Serie A performances after they missed out on a chance to move into the top four with a 1-0 home loss to Monza.
Luca Caldirola's 78th-minute finish was enough to give the visitors an upset victory at San Siro and further extend the Nerazzurri's barren league run.
Inter have collected just one point from five Serie A games, damaging their hopes of Champions League qualification. The defeat saw them fail to capitalise on a draw for city rivals Milan against Bologna earlier on Saturday.
Speaking afterwards, Inzaghi reflected on another tough result for his side, noting he feels they are doing little wrong but must be smart to find answers.
"We got nervous," he told DAZN. "We want this victory, but it is not coming in the league at the moment.
"A mature team must stay in the game. We need to direct the game.
"Now we're talking about a defeat that has slowed down [any chance of momentum]. We have to work on it and not just up front.
"After Lisbon, I was calm. But then, we have seen how it has gone.
"But we lose games that we do not deserve to lose, so we still have to be rational."
With eight top-flight games to go and just a two-point gap to third-place Roma, Inter's top-four hopes are far from over.
In addition, they still have the second leg of their Champions League quarter-final tie with Benfica to come this week, having taken a 2-0 victory on the road in Portugal.
Inzaghi accepts there is a tough spell ahead, and says both he and Inter must be frank in their self-appraisal if they are to turn matters around.
"We're behind in the league, but we have time to recover, even if these are heavy [blows to take]," he added.
"This result is not deserved but we need to make more of an impact on games.
"We were the best attacking side in Italy, but now we have difficulties. We have to do a mea culpa, including myself as the coach."
