In the context of Project Management Professional (PMP) practices, when a key function is anticipated to take longer to complete, the project manager should engage with the project team to review options and possible solutions. This approach aligns with the principles of iterative planning and agile methodologies, which emphasize collaboration, team engagement, and adaptive planning to address changes and challenges that arise during project execution. It is essential to work with the team to understand the issue's impact on the project's schedule and scope and to explore all possible avenues to mitigate delays while maintaining quality and meeting project objectives.
References: The answer is verified by the principles found in the PMI's guide to the Project Management Body of Knowledge (PMBOKGuide) and the Disciplined Agile (DA) toolkit, which advocate for a collaborative approach to problem-solving within the team and adapting plans as necessary based on the team's velocity and iteration goals12.