Newcastle have seen it from both sides, of course.
Just as Isak is training away from the group on Tyneside, Newcastle target Yoane Wissa previously had a stint working on his own at Brentford.
Newcastle identified Wissa as a potential replacement for Callum Wilson, who left following the expiry of his contract last month, and the club have had a fresh bid turned down for the DR Congo international.
Trying to sign one quality frontman has proved difficult enough for Newcastle – let alone an additional centre-forward like Hugo Ekitike, Benjamin Sesko or Joao Pedro, who chose to move elsewhere.
Recruiting two heavyweight strikers in the final days of the window feels a huge ask, but there is also something far bigger at play here, too.
What sort of precedent would it set if Newcastle were to meekly wave off a player with three years left on his contract, especially to the champions?
Newcastle have instead held firm – rejecting a £110m bid earlier this month – and the club do not foresee the “conditions of sale” being met before the window shuts on 1 September.
If that proves to be the case, could there really be a way back for Isak after the away end called the 25-year-old”greedy” and sang about him “not caring about us” at Villa Park last week?
Thomas Concannon, a member of the Wor Flags group, who helped put together the Alexander the Great tribute display last season, has been left “bewildered” by Isak going “completely nuclear”.
But the Geordie, like the club, has not closed the door on the Swede being reintegrated.
“I don’t think Newcastle are going to be able to find any suitable replacement at this stage,” he added. “If anything, that’s where Isak’s frustration should be because there was a possible suitable replacement [Ekitike], but Liverpool bought him instead.
“I do think there is a way back because, ultimately, he has to play football. If he scored a few big goals, I think some would be willing to forgive.
“He has burned bridges, but my personal opinion is if he scores some big goals and starts playing well again, that would go a long way.”