Manager Roberto Mancini was not satisfied with Inter's 1-0 second-leg win over Celtic in the Europa League on Thursday , saying his side "must improve in every respect."
Inter held an advantage on away goals after a 3-3 first leg, and Celtic went down to 10 men after Virgil van Dijk was dismissed in the first half.
But much to the chagrin of Mancini, Inter could not take the lead until two minutes from time, when Fredy Guarin broke the tie with a late strike.
"There was a big risk at the start, as a goal then would change the game," Mancini told Mediaset.
"With the red card, it became easier. We are getting better, but still make mistakes in every single match. When we don't make mistakes any more, then we can say we're better off.
"We should've scored earlier to relax into the game. Guarin has always been able to shoot like that. Maybe in the past he got too bogged down carrying the ball, but his runs from deep are dangerous."
Inter may have advanced to the last 16 of the Europa League, but Mancini's men are in eighth place in Serie A, 10 points out of the Champions League places.
"We must improve in every respect. We are making progress and will try to run fewer risks in defence, ensuring the midfield protects them more.
"Celtic were more locked down today and didn't allow us the same spaces we had in Glasgow. When they attacked, we weren't quick enough to cover the gap between midfield and defence, as Hernanes and Guarin stayed too far forward."
Celtic boss Ronny Deila gave a scathing analysis of referee Ivan Kruzliak's performance.
The Celtic boss described the sending off as "very cheap" and said of the Slovakian official: "He had a bad day at work, that's for sure."