The Foxes were already guaranteed their place in the last 16 of the Champions League but they were humiliated by a Porto side who dominated from start to finish at Estadio do Dragao as they secured the runners-up spot in Group G.
Claudio Ranieri made the decision earlier this week to rest a number of his first-team players but it soon became clear that their replacements may struggle to compete with their hosts in Portugal.
Diogo Jota could have doubled his team's lead three minutes later, only to drag his low strike wide of the post from 20 yards, but Porto were soon able to net a second when Jesus Corona volleyed into the top corner from 14 yards out.
Leicester began to offer a small threat through the pace of Schlupp and Ahmed Musa but Porto were soon back on the offensive, and Yacine Brahimi should have found the target when working a chance for himself just inside the 18-yard box.
However, a minute before the break, the Algerian international had his goal when he flicked the ball into the far corner after meeting Maxi Pereira's cross from the byline.
Ranieri introduced both Leonardo Ulloa and Marc Albrighton at half time and it was Albrighton who added an immediate spark in the final third, with his cross causing confusion in the penalty area before Demarai Gray volleyed over.
It was not long until Porto got back on top, though, with Jota shooting just wide of the far post after turning Marcin Wasilewski while Brahimi forced a solid stop out of Hamer from 20 yards.
However, Porto did extend their advantage in the 64th minute when Silva netted from the penalty spot after Danny Drinkwater had pulled the striker down in the box.
Leicester were dealt a further blow when Drinkwater went off injured, although his replacement Harvey Barnes was given the chance to make his first-team debut in a Champions League fixture.
It continued to get worse for his side, however, as Porto scored a fifth through Jota, who was played in on the edge of the penalty area before he sent a shot through the legs of Hamer.
Ulloa struck the crossbar for Leicester as they rallied briefly at the end of the match, but the game had been over as a contest since Porto's second goal and Ranieri has work to do in order to prepare his team for their Premier League clash with Manchester City at the weekend.