AC Milan lost 3-0 to rivals Inter in the Italian Supercup final and suffered a 1-0 defeat to Torino in the Coppa Italia last 16, while they drew 2-2 with AS Roma and 2-2 with Lecce in their last four games in all competitions.
Pioli's side sit second in the league standings on 38 points after 18 games, 12 points behind leaders Napoli who have played a game more.
"We have to face these difficult moments, it will be another test to overcome with unity and humility," Pioli told reporters on Monday.
"The criticism is fair because our performances in this period are below our expectations, which are very high because we are AC Milan.
"We have endured experiences where we faced everything with more ease, now we need compactness and the will to react. There have been 10 difficult days, in which we played a lot, more than usual. I have a lot of confidence in my players."
Pioli said AC Milan will seek to be consistent throughout the game when they face Maurizio Sarri's Lazio, who are sixth on 34 points.
"Lazio are doing very well in the league, they are on the rise from last year and are led by a top coach. We know them, they know how to dribble well but also attack with speed and quality," Pioli said.
"Both teams will want to control the course of the match, so we will have to be more determined and solid. I expect to see a very attentive and focused team, in addition to the game plan it is also important to have continuity throughout the 90 minutes."
