Osimhen could only provide the penalty to Napoli's second goal as they were defeated 3-2 at the Armando Maradona Stadium in Naples against Real Madrid.
The matchday two fixtures of the UEFA Champions League group stage got underway on Tuesday night across different centres with the away teams seemingly having the upper hand in more of the games.
In Naples and Manchester, the scorelines were identical with Napoli and Manchester United both falling to 3-2 home defeats against Real Madrid and Galatasaray respectively.
For the game at the Armando Maradona Stadium in Naples, Nigeria's Victor Osimhen was caged and couldn't get any goal in the five-goal thriller.
The 24-year-old however made a valuable contribution winning a penalty kick that resulted in one of Napoli's goals against Los Blancos.
The Naples-based side started well, scoring first in the game with Leo Ostigard's header but they were soon subdued by Carlo Ancelotti's men later in the game.
Jude Bellingham created an assist for Vinicius Junior before scoring a solo goal to put Real Madrid.
Though the penalty kick won by Osimhen and scored by Piotr Ziellinski pulled Napoli levelled at some point, an unfortunate own goal by goalkeeper Alex Meret ensured Real Madrid returned to Spain with the maximum point.
Thriller in Naples
It was Napoli who had the first attempt on goal in the fifth minute from Zelinski's shot that was parried by Kepa.
And two minutes later, Jude Bellingham sent a pocket pass to Rodrygo whose effort was parried by Alex Meret.
The deadlock was then broken in the 19th minute by Leo Ostigard, who jumped higher to head in Nathan's cross.
The lead was short-lived in the 27th minute when Bellingham offloaded the ball to Vinicius Junior who then slotted into the far corner of Meret.
Bellingham then put the visitors in front with his solo effort, having dribbled past four Napoli players, he played the ball sideways of Meret in the 34th minute.
Bellingham's goal made him the third player after Christian Kerembu in 1998 and Cristiano Ronaldo in 2009 to have scored in two consecutive Champions League games.
And five minutes later, Osimhen's attempt on goal from a header to Politano's cross was saved by Kepa.
But the second half started on a brighter note for Osimhen's side and in the 52nd minute, a VAR decision awarded the hosts a penalty after the ball caught up with Nacho's hand while defending Osimhen in the box.
Piotr Zielinski then sent the spot-kick into the net two minutes later.
Unfortunately for Napoli in the 78th minute, their goalkeeper Alex Meret scored an own goal which turned out to be the deciding goal in the showdown.
Manchester United suffer second consecutive defeat at the Old Trafford
What could have been an evening of solace for Manchester United turned sour after they gave away the lead twice before losing 3-2 to Galatasaray.
This is their second loss to a Turkish side on home soil after Besiktas in 2009.
The Red Devils also lost Casemiro to a red card as they succumbed to their second consecutive defeat in the Champions League.
Manchester United summer signing Rasmus Hojlund scored a brace in the first and second half respectively but it wasn't enough as Wilfred Zaha punished his former club and Mario Icardi scored a winner against his former teammate, Andre Onana.
Elsewhere at the Stade Bollaert-Delelis, Arsenal couldn't continue their riot in the Champions League as they were defeated 2-1 by Lens.
The Gunners scored first in the 14th minute from Gabriel Jesus' finish to Bukayo Saka's assist. But while it would have looked like an easy ride for the London side, they conceded in the 25th minute with Adrien Thomasson and 69th minute Eyle Wahi.
At Denmark, what could have ended Bayern Munich's group-stage dominance took another twist as they came back to a 2-1 victory over Copenhagen.
After a barren draw between both sides in the first half, Lukas Lerager gave the hosts a lead in the 56th minute but Jamal Musiala responded with an equaliser 11 minutes later.
The winning goal came from last Wednesday's winner against Manchester United super substitute Mathys Tel in the 83rd minute.
Also on Tuesday, Sadiq Umar and his Real Sociedad teammates secured a 2-0 win away to FC Salzburg.
Meanwhile, Inter Milan got a solitary win over Benfica at the San Siro while Sevilla and PSV Eindhoven played a 2-2 draw in Seville.