Sheffield Wednesday fan Jamie Vardy put the Blades to the sword as Leicester knocked Sheffield United out of the FA Cup.
Sheffield-born Vardy, released by the club he supports at the age of 16, had been the target of "Owls reject" taunts by the visiting supporters, but he had the last laugh when he headed the only goal of the game after 66 minutes.
The fifth-round tie was the first game the striker had started in this season's competition, having previously played just 10 minutes of the replay against his former club Fleetwood last month.
Leicester boss Claude Puel also saw fit to play all his other big hitters, paying full respect to the Championship challengers as he named a full strength team.
That meant Riyad Mahrez made his return to the starting line-up - and was back at the King Power Stadium - for the first time since going AWOL after the collapse of his proposed transfer to Manchester City.
The Algerian received a warm reception from the Leicester fans, and a standing ovation when he was substituted late on, but was slow to get into the match as Sheffield United proved competitive opposition, playing tidy football but without really threatening Kasper Schmeichel.
Vardy got his first glimpse of goal after 10 minutes. A good first touch from Wilfred Ndidi's pass set up the shooting opportunity, but his effort from the left side of the penalty area was deflected over the crossbar by Jake Wright.
Shortly afterwards, from a similar position, Vardy curled an attempt narrowly wide of the far post.
Sheffield United goalkeeper Jamal Blackman was worked for the first time midway through the first half when he had to push away a 25-yard strike from NDidi.
Despite being under pressure for the most part, the visitors had a golden chance to take the lead just after the half hour mark. Samir Carruthers' deflected cross saw the ball drop invitingly for Enda Stevens 10 yards out, but former Blade Harry Maguire slid in to make a last-ditch block and prevent an almost certain goal.
Vardy was presented with a third chance from the left side of the area when Mahrez put him through one-on-one with Blackman. He hit the target this time, but the onrushing goalkeeper made the save with his legs.
Leicester tried to maintain their pressure in the second half, but they were largely kept at arm's length.
Mahrez and Demarai Gray were menacing on the break and Vardy's pace in behind the defence was always a danger, but the visitors were marshalling the threat well until Mahrez got free down the right and clipped a cross to the far post where Vardy looped a header back across goal and into the net.
Blackman denied Gray a quick second goal before opposite number Schmeichel kept his side ahead and ensured they progressed to the quarter-finals with a good save to thwart George Baldock as Sheffield United posed a rare threat.