Los Txuri-Urdin have added Takefusa Kubo, Brais Mendez and Mohamed-Ali Cho to their squad this summer to offset the losses of Adnan Januzaj, Willian Jose and Alexander Sorloth.
The Magpies are looking to add another forward and a winger to their ranks in the ongoing transfer window.
And Isak is still on their shortlist as a transfer target, with Newcastle keeping their interest in signing him alive.
Newcastle had a bid of around £40m for the 22-year-old rejected earlier this summer, with the Basque team believing he is worth around £50m.
It has largely been a frustrating transfer window for the Magpies, who were quoted inflated fees for every offensive target they pursued thus far.
The Anoeta outfit will travel to Cadiz for their opening La Liga fixture on Sunday while Newcastle will travel to Brighton on Saturday after beating newly promoted Nottingham Forest 2-0 at home.
It remains to be seen if they agree a transfer with the Magpies at the eleventh hour or if Isak will play his football in San Sebastian.
Newcastle have a number of targets in their crosshairs but with the transfer window nearing its close, the Magpies will have to work overtime to hand manager Eddie Howe another striking option.
