Having drawn 2-2 against Lecce in Pioli's first match, Milan went down 2-1 to Roma on Monday (AEDT) as Davide Calabria's error gifted Nicolo Zaniolo a winner.
Calabria's introduction in place of the struggling Andrea Conti had looked a masterstroke by former Inter boss Pioli three minutes earlier, when the full-back crossed for Theo Hernandez to cancel out Edin Dzeko's opener.
Although Pioli already seems to have imprinted an improved attacking philosophy on the Rossoneri since replacing Marco Giampaolo, the results are yet to follow, and Milan's coach did not hide his frustration.
"I expected more, yes. Over the two games, we frankly gave our contribution to the failed victories," Pioli told Sky Sports Italia.
"We made mistakes that were too obvious for a club of our status. We had done well enough in the first half and ran few risks, but the game would've been more in our favour had we not given away that goal.
"There's no point denying it, the situation is negative right now and we keep making clear errors. The most evident errors were on the two goals, but they weren't the only ones.
"I saw the performance as a step backwards compared to the Lecce game last week. If the ball moves slowly from the back, it becomes difficult to create any spaces.
"With a little more focus and concentration, we could've kept the match in the balance for longer. We were imprecise and paid the price for that."
Despite being annoyed by Milan's sloppiness, Pioli added he has no questions over the squad's attitude.
"I don't think we lacked determination, but we made too many wrong decisions and that is costly against a side on the same level as you," he said.
"We needed to play better on a technical level, with more precise passing, and we just didn't do that.
"I believe we have the quality to be more dangerous in attack than we were and to be more solid than we were. At this level, the games are in the balance and the slightest detail can make the difference.
"I don't believe we were negative or lacking in courage, but we conceded goals in avoidable situations."