Leicester beat Porto in their first home Champions League game to maintain the winning start to their first season in Europe’s premier club competition.
Islam Slimani, who had a prolific scoring record against Porto with his former club Sporting Lisbon, headed the only goal from a Riyad Mahrez cross.
Porto substitute Jesus Corona hit the post, but the Foxes held on.
Leicester lead Group F by two points from second-placed FC Copenhagen, who they meet on 18 October.
Slimani slays the Dragons again
Slimani, a deadline-day signing for a Leicester club record £29m, tormented Porto so much during his time with Sporting that he earned the nickname “the Dragon Slayer”.
In three previous matches in 2016 alone, the Algeria international had netted five times.
Here, he met the teasing, curling cross of the excellent Mahrez, diving towards the ball at the back post to head past a reluctant Iker Casillas.
It is his third goal in four games for the Foxes, all of which have been scored with his head.
Leicester, last season’s surprise Premier League champions, have made an uncertain start to the defence of their title, losing three of their opening six games and conceding four goals in defeats by both Liverpool and Manchester United.
Yet the template that brought success last season – a deep, solid backline and pacey counter-attacks – was once again employed with success at a raucous King Power Stadium.
After seeing his side leak three goals to corners at Old Trafford on Saturday, Leicester boss Claudio Ranieri preferred Luis Hernandez to Danny Simpson at right-back, but it was centre-halves Wes Morgan and Robert Huth who impressed.
At the other end, Mahrez caused trouble on the right in the first half, Vardy explored the channels and Slimani barely stopped running.
For two-time European champions Porto, a domination of the second half – they had eight attempts on goal to Leicester’s three – only brought serious pressure in the dying moments.
Indeed, until a frantic, backs-to-the-wall final 10 minutes, a low save from Hector Herrera’s long-range effort was the biggest test of the returning Kasper Schmeichel in the Leicester goal.
But, as Porto pressed, the Foxes were pushed deeper and goalmouth confusion became commonplace, with Corona’s back-post effort deflecting off Marc Albrighton and on to the woodwork.
As the tension increased, a flurry of late corners was not enough for Porto to improve a dismal record in England that extends to 17 games without a win.
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