Further to his struggles for fitness, the fallout of his move is clearly having an impact on Isak's personal well-being.
The fractious nature of his departure from Tyneside prompted the striker to invest £30,000 in guard dogs for his new home, as he revealed he received death threats in the aftermath of his transfer.
After appearing as a second-half substitute in Sweden's 4-1 drubbing at the hands of Switzerland earlier this week, Isak opened up on his frustrations at his current predicament. However, he stopped short of giving himself a free pass for his performances on the pitch.
Isak said: "It’s always frustrating when you’re injured. Regardless of whether it’s one match or more. It’s always worse for the player himself.
"It hasn’t been optimal. But when I’m on the field, I don’t give myself any excuses. I always want to play my game and perform. But yes, it’s hard to be away and not be able to help and contribute. Now I’m back and I’m positive. There’s not much that’s easy in football. But with experience, you learn to deal with things. That’s how it is with injuries and all that. You learn to deal with it and get back on track the right way."