The Nigeria international has been tipped to end his Partenopei stint ever since finishing as the top scorer in the 2022-23 Serie A season, spearheading Napoli to the title with 26 top-flight goals.
Osimhen experienced a downturn in fortunes last season, but interest in his services did not dwindle, and Napoli tied him down to a new contract with a hefty £113m release clause.
However, that renewal was more about protecting the striker's value than being indicative of where his long-term future lay, and president Aurelio de Laurentiis confirmed earlier this summer that Osimhen wanted to leave.
As Arsenal quickly dropped out of the running due to the cost of a deal, Chelsea, Paris Saint-Germain and clubs in Saudi Arabia soon positioned themselves at the head of the queue in the last knockings of the window.
Osimhen 'to stay at Napoli' after Chelsea wage offer
Despite losing Goncalo Ramos for a few months to a severe ankle injury, PSG did not firm up their interest in the Nigeria international either, leaving Chelsea and Al-Ahli to butt heads directly.
On Friday morning, it was reported that Al-Ahli had come to an agreement with Napoli over a deal worth around £67m, but Osimhen - who could have earned around £33m a year in Saudi Arabia - never gave the green light to a deal.
Less than an hour after agreeing a fee with Napoli for Osimhen, Al-Ahli incredibly shook hands with Brentford over a £40m deal for Ivan Toney, who has said yes to the move and completed his medical in London earlier today.
Toney's imminent switch to Al-Ahli left the Osimhen door open for Chelsea, but according to RMC Sport, the former Lille man has decided to stay at his current club after all.
The French publication claims that Chelsea offered him a weekly wage of £130,500 a week - much less than he could have pocketed in Saudi Arabia - but he has turned his nose up to a move to West London.
What next for Osimhen after transfer decision?
There is never a dull moment on transfer deadline day, especially not for those of a Chelsea persuasion, as the Blues prepare to end the summer window without capturing that all-important number nine.
However, there is now an even bigger story brewing in Naples, the one where Osimhen's decision to stay at Napoli could potentially see the Nigeria international not play any competitive football for months.
Due to the relentless transfer speculation, new Napoli boss Antonio Conte made it clear relatively quickly that Osimhen was not part of his immediate plans, and he was effectively replaced when Romelu Lukaku touched down in Italy.
Whether Osimhen will now be re-integrated into the Napoli squad is the question on the Partenopei faithful's lips, as freezing out a striker with 76 goals and 18 assists in 133 matches for the club is unfathomable.
Keeping the 25-year-old in exile would not be beneficial for any party involved, as while Osimhen would lose match sharpness, Napoli would see his transfer value plummet ahead of a likely exit in 2025, when he could enter the last 12 months of his terms.