Claudio Ranieri will demand answers from his Leicester City players after they capitulated to suffer a 4-1 defeat at Manchester United.
The champions were put to the sword by a United side shorn of sluggish captain Wayne Rooney in Saturday's early game - Chris Smalling, Juan Mata, Marcus Rashford and Paul Pogba putting the hosts in charge by the interval.
Three of United's goals were scored from corners, with Ranieri particularly irked by Rashford's - the product of a quick set-piece that caught Leicester's defence cold.
It was the second 4-1 defeat suffered by the Foxes early in their defence of the Premier League title, having gone down by the same scoreline away to Liverpool earlier this month.
"This is a very good lesson for us because when you concede a goal, it's important to maintain your composure, stay calm because sooner or later we can score," Ranieri said.
"Now we have to recharge our battery, immediately forget this defeat and look forward."
Demarai Gray's superb strike got Leicester on the board, but they have now lost all three of their away games in the league this term.
Porto visit the King Power Stadium in the Champions League on Tuesday and Ranieri has implored his players to remember the roots of their success from last season.
"It was the same when we conceded a goal at Liverpool. This is the second time," he added.
"I want to speak with my players: "Why, why?"
"Because, OK, if we lose we can lose, but it's important to maintain our mentality, our shape because that's our strength.
"I understand they want to show their character, but if you play alone, you play against 11. It's important you stay together and play 11 v 11."