Riyad Mahrez fired Leicester to the brink of the Champions League knockout stages after a 1-0 victory over FC Copenhagen.
The winger grabbed the winner to maintain the Foxes' 100 percent record in Europe and keep them top of Group G.
They are five points clear of Porto, the 2004 winners, and five and nine points ahead of FC Copenhagen and Club Brugge respectively with three matches remaining.
Victory in Copenhagen in two weeks would put the Foxes through to the last 16 but they needed Kasper Schmeichel, who is yet to concede a goal in the competition, to produce an outstanding late save to thwart Andreas Cornelius.
A third straight Champions League win is in stark contrast to their Premier League form and Claudio Ranieri's side have more points in Europe, nine, than they have domestically, eight.
But they are revelling in their European tour and ended Copenhagen's 23-match unbeaten run which stretched back to May.
Cornelius went close in the first half for the visitors and Islam Slimani also had a goal disallowed for the hosts. The Foxes could be punished by UEFA though with flares set off in the visiting section.
Mahrez had been recalled after starting Saturday's 3-0 defeat at Chelsea on the bench as Ranieri prioritised Tuesday's game although he was made to wait for a breakthrough during a scrappy half.
Following comfortable and deserved wins over Club Brugge and Porto, FC Copenhagen offered the Foxes a sterner test with the visitors six points clear in the Danish Superliga.
Tidy and efficient they started well, pressing the hosts and breaking at pace to underline the heightened danger for Leicester following two relatively straightforward wins.
With Leicester sloppy in possession the misfiring Jamie Vardy and recalled Slimani had little early service, although Vardy did see a deflected effort skid wide after 18 minutes.
Schmeichel comfortably claimed Federico Santander's low strike and slowly Wes Morgan and Roberto Huth got to grips with FC Copenhagen who, for all their organisation, struggled to make serious inroads against the Foxes.
Both teams cancelled out each other as the Foxes continually went long and looked out of ideas before they finally worked the ball wide and were rewarded with a 40th-minute winner.
All of the joy Vardy had got came from the left flank and when he was given time the striker launched a deep cross to Slimani.
The Algerian nodded down for the onrushing Mahrez, who escaped Mathias Jorgensen, to stab in his third Champions League goal of the season from six yards.
But FC Copenhagen almost hit back instantly when Youssef Toutouh's strike hit Morgan to loop onto the roof of the net and, from the resulting corner, Cornelius' header dropped inches wide.
The former Cardiff striker then almost caught the hosts out with a clever flick after the re-start.
Despite their lead Leicester were still not at their fluent best but thought they had doubled their lead after 67 minutes only for the offside flag to deny Slimani a second.
It would have given them breathing space but, after a tricky start, the Foxes had shut down FC Copenhagen and left them feeding off scraps.
There was little second-half reaction and with Mahrez leading any charge to find a second, the visitors became more concerned with stopping the Algeria international.
But they began to mount a late recovery and William Kvist fired straight at Schmeichel with eight minutes left before Santander's header was deflected over.
Schmeichel was called on to make a stunning save with a minute left to secure the points when he brilliantly changed direction to keep out Cornelius' low 10-yard strike.