The Partenopei are 14 points clear at the summit of Serie A, so the Scudetto is effectively in the bag, thanks in no small part to Osimhen, who has struck 21 times in just 24 league games this season.
However, Napoli's hopes of continuing their historic run in the Champions League are hanging by a thread after last week's 1-0 loss to AC Milan.
Luciano Spalletti's side had 16 shots at San Siro and yet somehow never really looked like scoring - not without Osimhen on the pitch, at least.
Strength in depth is undeniably one of the reasons for Napoli's Serie A supremacy this season. During the first half of the campaign, Giovanni Simeone and Giacomo Raspadori both stepped up whenever Osimhen was out.
However, Raspadori is still trying to regain his best form after his own spell on the sidelines, while Simeone is injured at the minute.
So, Osimhen's return to full fitness after picking up an injury on international duty could not have come at a better time for Napoli, for a couple of reasons.
Firstly, his mere presence on the pitch makes a monumental difference to his team's attacking threat. Napoli turned in a worryingly poor performance in last Friday's 0-0 draw at home to Verona, but as soon as Osimhen entered the fray late in the second half, they suddenly looked capable of making the breakthrough.
The 24-year-old attacker actually very nearly broke the crossbar with a stunning strike from just outside the area - less than 10 minutes after his introduction.
Consequently, that brief - albeit unsuccessful - cameo has renewed optimism among the fans ahead of Tuesday's second leg at the Maradona. Which brings us on to our second point.
While Osimhen was out of action, some of Napoli's ultras began a protest against their own club over ticket prices and stadium restrictions. The net result was some supposed supporters refusing to cheer on the team during the 4-0 league loss to Milan.
After Napoli were then beaten by the same side at a raucous Giuseppe Meazza last week, Spalletti pleaded with his own club's supporters to generate an equally vociferous atmosphere in the return leg. If that call was to fall on deaf ears, the frustrated coach said he would go home.
Happily, a truce appears to have been called in this self-destructive civil war, with the ultras and De Laurentiis having held successful peace talks over the weekend.
The hope, then, is that a re-united Napoli and returning Osimhen can propel the club into the semi-finals. Certainly, after the doom and gloom of last week, a comeback now seems possible.
As Spalletti said himself, "Victor is a hero of these fans now, so there is always a wave of enthusiasm around him."