When a key stakeholder introduces a new requirement, it is essential for the project manager to request further clarification. This ensures that the requirement is fully understood and its impact on the project schedule can be accurately assessed. The PMBOK Guide emphasizes the importance of clear communication and understanding stakeholders' needs for successful project management1. Additionally, the PMI-PBA highlights the need for detailed requirement analysis to manage changes effectively and align them with business objectives2. References: * Stakeholder Analysis: Pivotal Practice to Project Success | PMI1 * PMI Professional in Business Analysis (PMI-PBA) Handbook2