Palace sit 14th in the Premier League table, just two points clear of the relegation zone, and there is growing concern internally that they could be dragged into a fight for survival unless the problems under Sage are addressed quickly.
The manner of the Brighton defeat has intensified scrutiny, but it has not been an isolated concern.
Even Palace's two league wins over Fulham and Nottingham Forest failed to provide complete conviction, while their defensive record has become a major source of alarm.
They have conceded 17 goals in the Premier League so far, more than any other side, leaving Sage with significant work to do to restore confidence in a team that is struggling to find consistency.
Sources indicate that Palace are not on the verge of making a change, but the head coach's position is increasingly under scrutiny.
There is an awareness that results alone will not necessarily be enough if performances continue to raise questions about the team's organisation and resilience.
The next three fixtures could prove particularly important. Palace face Besiktas in the Europa League before returning to Premier League action against Newcastle, with both the results and the manner of those performances expected to influence the club's thinking. Palace then face Fulham in the EFL Cup.
Pressure is building, and sources say a decision could come quickly if Palace fail to show signs of improvement. The hierarchy want to see greater conviction and evidence that Sage can turn the situation around, rather than allow the team's difficulties to deepen.
With the relegation zone only two points below them, Palace will not let the situation drift. There remains time for Sage to steady the club, but the Brighton humiliation has raised the stakes considerably.