Leicester secured a first home win of 2017 as Demarai Gray’s superb solo goal sealed an extra-time victory over Derby in their FA Cup fourth-round replay.
Andy King headed the hosts, who made 10 changes, ahead after Gray’s clever cross was nodded back across goal by Marc Albrighton.
Abdoul Camara’s free-kick forced extra time for Championship Derby only for substitute Wilfred Ndidi to restore the Foxes’ lead with a fantastic strike.
Gray sealed a deserved win with an angled finish after a fine run.
Premier League Leicester will now face League One Millwall in the last 16 on 18 February (15:00 GMT).
Claudio Ranieri has not had too much to cheer about lately as last season’s champions have been plunged into a fight for Premier League survival.
Yet the Italian was all smiles and applauded home fans as they chanted his name around the King Power Stadium soon after King’s opener.
Leicester, 16th in the table and one point above the relegation zone, face a battle to climb away from trouble but their first win since 7 January will at least provide them with some momentum.
A spirited Derby display – and a poor performance from the officials – made sure it was anything but a straightforward win.
The hosts should have won a first-half penalty when Ben Chilwell was sent sprawling inside the area by Richard Keogh but referee Mike Jones was not interested.
There was more controversy in the 85th minute when Derby keeper Jonathan Mitchell clearly handled outside his area but Leicester’s Ahmed Musa was booked for protesting after Jones dismissed the home team’s appeals.
Both teams seemed to have their eyes on this weekend’s games as they made 18 changes between them.
Musa was the only survivor from the Leicester side that started last weekend’s match with Manchester United even though the Foxes are not in action again until Sunday.
Derby, despite bringing 5,000 travelling fans, made eight changes, as they also rested players to aid their play-off push.
“I didn’t want to make eight changes. If the game was last night the team would have been totally different,” said McClaren.
However, pundit and former Leicester midfielder Robbie Savage was critical of the number of changes made by both managers.
He said: “If Derby County were playing three Championship games in a week and chasing promotion would they put this team out? It’s absolute nonsense. Play your best team.”
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