On Wednesday, it was reported that the Blues' search for attacking reinforcements had led them to the Sweden international, whom they had supposedly made an enquiry over.
Newcastle's Financial Fair Play situation means that they are under pressure to offload at least one big name before June 30, in order to avoid running the risk of breaching the Premier League's Profit and Sustainability rules.
However, the Magpies understandably regard Isak as a fundamental player after he struck 21 Premier League goals in 30 matches last season, only behind Erling Haaland (27) and Cole Palmer (22).
As a result, Newcastle have reportedly demanded that Chelsea fork out a club-record fee if they want to prise Isak away from St James' Park, eclipsing the £115m that they paid for Moises Caicedo last year.
Chelsea have held 'no talks' over Isak deal
Despite claims that Chelsea had tested the waters with an enquiry, journalist Fabrizio Romano claims that no talks have been held over a deal for Isak because of Newcastle's valuation of the 24-year-old.
Romano adds that negotiations have not been held over moves for Crystal Palace's Michael Olise and Athletic Bilbao's Nico Williams due to the same reason; the former has decided to join Bayern Munich anyway.
As Isak - who has conjured up 35 goals in 67 appearances for Newcastle - still has four years left to run on his contract, it would supposedly take a 'crazy' proposal for the Magpies to consider letting him depart.
Arsenal are believed to have cooled their interest in the former Real Sociedad man for that exact same reason, and Isak himself has affirmed that he has no plans to leave the club in the near future.
What other strikers are Chelsea looking at?
While a move for Isak appears to be off the cards, Chelsea are said to be on the verge of bolstering their attacking ranks with the capture of Barcelona 18-year-old Marc Guiu for a meagre £5m.
The teenager is available for a modest price due to a clause in his contract, which Chelsea have reportedly agreed to trigger, although his arrival will not stop them pursuing a more seasoned centre-forward.
New Blues boss Enzo Maresca will likely see Romelu Lukaku and Armando Broja depart in the coming weeks, while Deivid Washington is yet to be given the chance to show what he is capable of in the final third.
Lille's Jonathan David is thought to be a prime target for Chelsea amid claims that he could be available for as little as £20m, as he has no plans to extend his contract with the French side, which runs out in 2025.
However, the Blues are just one of four teams pursuing the Canada international, who is also being monitored by West Ham United, Manchester United and Tottenham Hotspur, the latter two of whom could offer him Europa League football.
Hoffenheim youngster and Germany Euro 2024 international Maximilian Beier is believed to be of interest too, and Victor Osimhen's next club has still not been decided, but his £113m price tag will likely put Chelsea off too.