Against all expectations, that feeling is back. Leicester's achievement in reaching the Champions League quarterfinals with a nervy, come-from-behind 3-2 aggregate win against Sevilla is all the more remarkable because the team's genie had, by any stretch, seemed to be out of the bottle. Craig Shakespeare's reversion to the setup that served them so well a year ago was the obvious fix to their problems after six months of over-elaboration by Claudio Ranieri. But if a return to old methods made good sense, the task involved in recapturing the spirit, both on and off the pitch, that had carried them home before seemed far steeper.

From staring into the abyss a mere three weeks ago, Leicester have produced perhaps the most famous single result in their history. They earned it by remembering their major strength: the ability to turn matches against more technically adept opponents into battles, fought at a raging tempo, and overcome them using sheer energy and flourishes of quality at key moments.

"In a cup tie of this stature, against one of the best teams in Europe, we needed to make sure we kept a cool head," Shakespeare said in his postmatch news conference. "But we needed to show that competitive edge and I think we did from the first minute. That was our game plan: to press high up and make life uncomfortable for Sevilla. We didn't want them to play their passing game and I think you could see that."

Nobody could fail to miss that. Leicester were relentless and not only because Jamie Vardy -- playing on the edge of legality but setting about his job with an urgency and snarling aggression that unsettled Jorge Sampaoli's side from the beginning -- looked like a player fighting for his career at the highest level. At 30, how many times would this chance come around again? If it was gamesmanship from the striker that aided Leicester's cause in luring Samir Nasri to a red card, it was hard not to feel admiration for the sheer force of will that had driven him all evening.

Leicester players celebrate at full-time of their 3-2 aggregate win against Sevilla in the Champions League.

Perhaps it was no coincidence that the first of Nasri's two yellow card-worthy transgressions was against Wilfred Ndidi. At this rate, the 20-year-old can become a better player than N'Golo Kante, who he has effectively replaced; his pitch coverage was comparable while his anticipation and composure on the ball gave Leicester a foothold in a midfield tussle that could easily have been lost. If any two players stood out in a gargantuan collective effort from Leicester, it was Vardy and his younger teammate. Shakespeare suggested that this was a result born of momentum rather than a one-off blast from the past.

"The first win [of his tenure] against Liverpool was key; you can see the confidence," he said. "Then in the Hull game [a 2-1 win] it was important to go on a winning stream. When you lose, players will lose confidence -- and we needed to get back to winning ways as soon as possible."

In picking the same starting XI for three consecutive games, Shakespeare had selected players who had experience of winning. Against Liverpool and Hull, they remembered the way to do it; against Sevilla, they harnessed that energy to find a head of steam that appeared to have vanished out of view forever.

It means there can be no telling, with any degree of confidence, what lies in store next. Leicester have tripped everyone up on enough occasions now; Shakespeare knows it and was happy to suggest his team can be the unknown quantity in a last-eight that, the Foxes apart, will contain established Champions League powers.

Jamie Vardy got under Samir Nasri's skin enough that Frenchman was ultimately sent off in the 74th minute.

"We know there are going to be some terrific teams and we have to be delighted with knocking Sevilla out as their record is there for everyone to see," Shakespeare said. "But we're there on merit, make no mistake about that, and we might just be the surprise team. We know the quality of the teams in there is getting down to the serious business now."

Perhaps Leicester, who only had 32 percent of the ball against Sevilla, will not be unhappy to face sides that, almost exclusively, covet possession. If nothing else, the established contenders will have been warned that a side with qualities they have rarely faced in this competition is coming for them with very little to lose and a renewed tide of goodwill behind them. Juventus legend Gigi Buffon seemed to suggest as much in his comments after the Old Lady breezed past Porto into the quarterfinals in the other match of the evening.

Shakespeare was gracious enough to give credit to Ranieri, noting that Leicester's 2-1 defeat in the first leg "gave us the springboard for the result tonight." In truth the two performances were light years apart and it seems impossible that Leicester would be dreaming of Bayern Munich and Barcelona now had Ranieri still been in charge. Sometimes you simply lose your way; it does not have to reflect terribly on anyone.

"I think as a football club we have to know our strengths," Shakespeare said. "You saw that in tonight's performance in terms of desire, and we can play a bit as well. I think tonight's performance epitomises what we're about."

Just as last season you could pick a different Leicester hero every week, against Sevilla you could pick a different one for every key stage of the game: Kasper Schmeichel for his penalty save; Riyad Mahrez and Wes Morgan for the free kick and finish that broke the deadlock; Marc Albrighton for his fizzing second goal; Vardy for driving those trailing him to distraction.

The genie is back in the bottle, Shakespeare has made sure of that -- and if a few more wishes are granted then the 2015-16 season may yet only have been the start of Leicester's assault on the history books.