Leicester City suffered the biggest margin of defeat by an English side in Champions League history after Andre Silva's double helped Porto secure second place in Group G with a resounding 5-0 victory at Estadio do Dragao.
Claudio Ranieri admitted Leicester face a scrap for top-flight survival following the 2-1 defeat at Sunderland last time out, but their sparkling, unbeaten form in Europe had represented a reprieve from what has been a dismal season so far.
However, the Premier League champions never looked likely to extend their unbeaten record on Wednesday, thanks to a comprehensive first-half display from Nuno Santo's side.
Silva capitalised on weak defending to put the hosts ahead early on, with Jesus Corona's exquisite volley and a deft finish from Yacine Brahimi doing further damage before half-time.
The result marks the heaviest defeat by an English side in Europe since Everton's 5-0 loss at Benfica in the 2009-10 Europa League, and represents another blow for struggling Leicester, who face Manchester City this weekend before they find out their Champions League fate in the last-16 draw on Monday.
With Leicester having already secured top spot in Group G, it was no surprise that Ranieri named a much-changed line-up given his side's terrible Premier League form.
But despite handing several of Leicester's fringe players chances to impress ahead of the clash with City, Ranieri saw his team go behind inside six minutes, when Champions League debutant Ben Hamer could only parry Brahimi's stinging effort wide.
Corona whipped in the resulting corner, shambolic Leicester marking allowing Silva to head home unchallenged.
Silva could have doubled his tally shortly after, but the 21-year-old failed to apply the finish after connecting with Alex Telles' cross.
Porto did have their second after 26 minutes, though - Telles' precise cross picking out Corona, who despatched a venomous, perfectly-executed volley into the top-right corner.
Santo's side continued to dominate, and deservedly extended their lead further on the stroke of half-time as Brahimi - making just his third start across all competitions this term - flicked home from close range at the culmination of a sublime move.
Ranieri introduced Leonardo Ulloa and Marc Albrighton at half-time, and the latter almost turned provider immediately following the restart, but Shinji Okazaki was unable to turn in the winger's cross.
Despite their renewed attacking vigour, Leicester remained hapless at the other end, Jota the next to try his luck with a low effort that flashed just wide.
Leicester were further behind just after the hour mark, Silva drilling home from the penalty spot after he had been brought down by Danny Drinkwater.
It got worse for Leicester - Drinkwater going off injured before, with 13 minutes remaining, Jota slotted home through Hamer's legs as Porto secured progression in style.
