The Swedish striker, a reported Liverpool target, returned to the Magpies' training ground yesterday after previously working out at his former club Real Sociedad's facilities.
The rest of the squad also returned yesterday from the Republic of Korea and were given time off. Isak also returned to England a few days later to resume training with the team.
Manager Eddie Howe organised a team event for today, including players' families and staff.
Isak trains alone
According to Sky Sports, as reported by Sportal, Isak was told to report to the training ground after everyone else had departed.
Many UK media outlets have suggested that Isak's potential move to Liverpool hinges on Newcastle securing a replacement.
However, the Magpies appear to be losing out on Benjamin Sesko, who is reportedly closer to joining Manchester United. Current alternative targets for Newcastle include Nicolas Jackson and Johan Wissa.
Meanwhile, Liverpool are on the verge of selling Darwin Nunez to Al-Hilal and will likely use the funds to make a new offer for Isak.
The Reds expect to receive a guaranteed £46 million for the Uruguayan, potentially rising to £56 million with add-ons.