Three of Napoli’s goals came from Arek Milik in the first half. Milik found the back of the net on 3 minutes, 26 minutes and scored from the penalty spot on 36 minutes. This made for a half time score of 3-0 in Napoli’s favour.
A penalty scored by the Belgian international Dries Mertens on 74 minutes added insult to injury for KRC Genk that finished the match 4 goals down. Having taken just 1 point from their 6 group stage games, KRC Genk finish bottom of their group.
Napoli finned second in the group with 12 points and have qualified for the knock-out stage.
Napoli sack coach despite convincing win
Napoli coach Carlo Ancelotti was sacked shortly after watching his side end a nine-match winless run in all competitions to reach the Champions League last sixteen on Tuesday.
His side, inspired by a first-half hat-trick from Arkadiusz Milik, outclassed Genk 4-0 in Group E but the 60-year-old was shown the door just three hours after the final whistle, with Italian media naming Gennaro Gattuso as favourite to replace him.
Napoli finished second in the table with 12 points, one behind Liverpool, while their Belgian opponents finished bottom of the group with one point. Salzburg came third to qualify for the Europa League last 32.
Genk's Maarten Vandevoordt, who at 17 years and 287 days became the youngest goalkeeper to play in the UEFA Champions League, had a nightmare start as he gave the ball away under pressure and allowed Milik to score in the third minute.
The Pole fired the second in the 26th minute and converted a penalty in the 38th before Dries Mertens, on his 300th Napoli appearance, completed the scoring with another penalty a quarter of an hour from the end.
Both Gazzetta dello Sport and Corriere dello Sport had reported before the game that Ancelotti was set to be fired whatever the result.
Ancelotti claimed after the game that he was still hopeful of keeping his job and that he was due to meet club owner and President Aurelio De Laurentiis on Wednesday.
"I hope to stay but that is a decision the president will make. This team has quality which they have shown in the Champions League but not in the league.
"They haven't said anything to me, I was just preparing the match. Will I resign? I've never done that in my life."
But just before midnight, Napoli issued a statement confirming his dismissal.
There was a downbeat mood right from the start of Tuesday's game when the hosts were greeted by a lukewarm reception, with the San Paolo stadium less than one quarter full.
But Napoli responded brightly, Kalidou Koulibaly scraping the crossbar immediately with a header.
Vandevoordt then collected a pass in his penalty area but was pressured by Napoli forwards and Milik had an easy job to score as the teenager lost the ball.
After Joseph Paintsil skimmed the post for Genk, Napoli went further ahead when Allan sent Giovanni Di Lorenzo down the right and his cross was turned in at the near post by Milik.
Allan then sent Calderon through and he flicked the ball over Vandevoordt, was tripped and Milik converted from the spot.
When Casper de Norre gave away another penalty with a handball it was Mertens who converted with a Panenka-style chip down the middle of the goal to complete Nepali's first win since Oct. 23.
Former Chelsea, Real Madrid and Bayer Munich coach Ancelotti led Napoli to second place in Series A last season but his team has suffered a loss of form this term and they fell out with De Laurentiis after he ordered the players to be confined to a week-long training camp.