Leicester City crashed to the heaviest defeat by an English team in Champions League history, prompting manager Claudio Ranieri to question their character.
"We can lose, but I want us to show our character and our strength," Ranieri said. "We didn't do that well enough tonight."
"We wanted to see something different tonight, but it was too easy for Porto to score."
Andre Silva hit a brace, while Jesus Corona, Yacine Brahimi and Diogo Jota also got on the scoresheet at the Estadio do Dragao.
— Leicester City (@LCFC) December 7, 2016
"The result is my fault because I decided to change the team. I don't regret it, but some players missed their chance."
Ranieri made 10 changes to the starting XI amid a poor run in the Premier League.
"I'm sad for our fans. They deserved more. I didn't see what I have seen in training on the pitch tonight."
"But I have a clearer idea about my players now. We need to focus on the Premier League and change our position."
The Foxes play Manchester City at the King Power Stadium on Sunday. Last year's champions have three wins from 14 games and sit 16th on the Premier League table, two points above the relegation zone.
Their run in Europe faces an uptick in intensity with Paris Saint-Germain, Bayern Munich and Real Madrid among their possible opponents when the round-of-16 draw takes place on Monday.