Head coach Matthias Jaissle is also facing questions over his methods after a disappointing start to his first season in English football, although there is reportedly no overwhelming desire among the players for him to be replaced.
Newcastle are 13th in the Premier League after their defeat by Everton, which followed their League Cup elimination by the same opponents. The result prompted boos from supporters and criticism from Jaissle, who accused his players of failing to follow his game plan.
However, there is a feeling within the dressing room that recruitment has been a major factor in the club's struggles. Newcastle United spent approximately £262.9 million on eight players during the summer after losing Bruno Guimarães, Sandro Tonali and Anthony Gordon.
Several of the new arrivals have yet to make a significant impact. Aladji Bamba, Bazoumana Touré and Matías Fernández-Pardo have struggled for opportunities, while Sean Steur is considered a player who will need time to develop. Amar Dedić and goalkeeper Lukáš Horníček have also had difficult moments.
One source told the Telegraph: “It's not that they are necessarily bad players, but they aren't ready for the Premier League. You can't rely on them yet. Put that together with a manager who hasn't coached in England before and it is a dangerous mix.”
There are also concerns about Jaissle's tactical approach, particularly his decision to operate with two central midfielders and a number 10. Newcastle have been exposed in the middle of the pitch, with one source arguing that the team needs an additional player in that area.
The manager's methods have prompted comparisons with former Manchester United head coach Rúben Amorim, who struggled to adapt his preferred system to his squad.
Despite the criticism, Jaissle remains generally well liked by the players and there is no clear consensus that changing the manager would solve the club's problems. The concern is that both recruitment and tactical decisions have contributed to an unsettled start.
The immediate challenge is a trip to Fulham on Saturday, with a difficult run of fixtures to follow after the international break. Newcastle then face Arsenal, Brighton, Manchester United and Sunderland.
In a separate assessment, Telegraph columnist Luke Edwards described the coming weeks as a defining period for Jaissle, arguing that the manager must quickly improve results and restore belief among supporters.
Edwards also highlighted the significance of the Sunderland fixture, pointing to the damage caused by Newcastle's defeats to their local rivals last season under Eddie Howe.
There are wider concerns at the club, with PIF representative Jacobo Solis having spent more than a week on Tyneside and held meetings with key figures. His presence has not been presented as evidence of an imminent managerial change, but the scrutiny on Jaissle is increasing.
The manager has had only a short time to implement his ideas, and the summer recruitment took place before his arrival. Nevertheless, Newcastle need an improvement before doubts over the direction of the rebuild become harder to contain.