John is a line manager at a medium-sized company in South Africa, and he oversees a team of five customer service representatives. One of his employees, Sarah, has been underperforming for the past few months. John has noticed that Sarah has been consistently missing her performance targets and making mistakes that are impacting the team's overall productivity.

John has attempted to address the issue with Sarah in the past, but he has not seen any improvement in her performance. He is now faced with a performance management problem that requires his attention. John has approached you - the HR manager - for advice on the way forward.

1.1 How can John identify the cause of Sarah's underperformance? From a performance management perspective, what steps can be taken to address the underlying performance issues and support Sarah in improving her performance? 1.2 What are the potential problems for John and the company for not addressing poor performance within a team?