Porto’s André Silva, right, scores the opening goal against Leicester City in the Champions League Group G game. Photograph: Paulo Duarte/AP

As chapters in a Champions League adventure go, this could hardly have been less romantic. Better sides than Leicester have fallen at Estádio do Dragão and it spoke warmly of their achievements to this point that Claudio Ranieri could afford to field a skeleton lineup for what could have been their toughest Group G assignment. The shame in this defeat, confirmed by two goals from André Silva either side of slick finishes from Jesús Corona and Yacine Brahimi before Diogo Jota completed the rout, is superficially slight but Porto could not have dreamed of more supine opposition against which to ensure their own progress. Any thoughts of a pick-me-up before Saturday’s critical meeting with Manchester City were exposed as fantasy.

Whether Leicester are in a position to allow the disappointments, however incidental, to pile up seems an increasingly relevant question. The intention was surely to enjoy nights on such an exalted stage more than this but instead the impression persists of accelerating poor form. Riyad Mahrez, Jamie Vardy, Robert Huth, and Islam Slimani were all left at home and their replacements came nowhere near a level that might shake their out-of-touch peers into better form. That it took Iker Casillas a full 31 minutes, at which point he was obliged to play a goal kick 20 yards to his right, to touch the ball, spoke amply of Leicester’s application.

The tone was set within six minutes. Ben Hamer, starting in goal for the first time since January 2015, might have appreciated the early warming of palms from Yacine Brahimi’s deflected cross but the resulting corner afforded him rather less practice. Jeffrey Schlupp certainly had Silva under close guard as Corona delivered but, preferring to shove rather than mount a challenge of note, was rooted as his opponent shrugged him off to nod past an exposed Hamer.

Porto’s single-goal win over Braga at the weekend had followed four consecutive scoreless draws and the statistic was made to seem a trick of the imagination. Jota, surging in from the left, fizzed a 20-yard drive wide of the near post and Luis Hernández stabbed away a centre from Corona. By the 20-minute mark Leicester had barely left their own half and such was their opponents’ domination that when Silva, lifting Maxi Pereira’s cutback over, missed glaringly shortly afterwards it was hard to sense any potential regret.

The impression was confirmed in thrilling fashion. Schlupp was again unconvincing in the challenge as Alex Telles bustled past him towards the left byline but there was plenty of work for Corona to do when the Brazilian’s cross found him beyond the back post. He made light of it; the volleyed connection, with the laces of his left foot, could not have been sweeter and nor could the ball have arced more perfectly into Hamer’s top corner.

Brahimi skewed wide but would not wait long for something more substantial. Leicester were operating at training pace, doing no service to the notion that individual reputations might be enhanced by bright showings here, and were carved open again a minute before half-time when the right-back Pereira was allowed to overlap untracked. The Porto players were queuing up but it was Brahimi, executing a difficult chance on the run, who backheeled cutely ahead of Hamer.

Schlupp’s replacement by Marc Albrighton for the second half was no surprise; Ahmed Musa’s by Leonardo Ulloa was more eyecatching for the simple reminder it provided that the forward had been on the pitch. The changes brought some early improvement, an Albrighton sortie resulting in Demarai Gray’s half-volley over the crossbar, but it quickly proved illusory.

Danny Drinkwater’s 64th-minute foul on Silva was punished by the forward’s unfussy finish from the spot, before Jota exposed Ben Chilwell to run through and finish comfortably 13 minutes from time. Ranieri could take heart from a full 90 minutes for Nampalys Mendy, the intended replacement for N’Golo Kanté, who had been injured since August, but Leicester need may more than a replica of last season’s lungbusting midfield heroics to play themselves back into shape.