Champions Inter dropped to second in the table with eight points from four games after they came from behind to play out a surprise 1-1 draw.
"We had difficulties against a team that played a good defensive game," Inzaghi told a press conference. "We had chances that we didn't convert, we made technical mistakes.
"Then in the second half we didn't do well, we didn't create dangerous situations, and when we switched to three (up front) we had this great goal from Dany Mota that created difficulties for us."
Inter intensified their efforts after going behind in the 81st minute and defender Denzel Dumfries equalised two minutes from time, but the time was not on their side as they tried to wrap up three points.
"We had a great reaction after the goal, maybe we should have had it earlier," Inzaghi added.
"We had a couple of situations that weren't exactly clear, usually we manage to capitalize on them. In games like this you have to try to unlock the result... If you stay tied and concede goals, games become difficult."
Argentine striker Lautaro Martinez had an early chance to put Inter in front but sent his header slightly above the bar.
Last season's Serie A top scorer remains goalless so far in the campaign.
"He had a little problem, he couldn't train a lot," Inzaghi said.
"The attack was the only department where I had one player, (Joaquin) Correa, in the last 10 days (in training). We thought we would find the goal sooner.
"The team was a bit slow but until (conceding) the goal (Yann) Sommer had no work. But you accept a goal like that more than the ones we conceded on the first match day, even tonight overall defensively we did well."
Inter drew 2-2 at Genoa in their season opener, before consecutive home wins against Lecce and Atalanta.
They get their Champions League campaign underway when they travel to Manchester City on Wednesday.
"I'm quite calm," Inzaghi assured. "I have all the players available, and this new Champions League is something new for all of us coaches.
"It's the first year (of the new format), there are two more games without the usual group. We'll have to try to do our best, any opponent we find in the Champions League is difficult."
Teams will play eight games in the 36-team league phase under the new competition format, which replaces the former group stage.