Make sure you read the article (from my other site) How To Handle Poor Performers. It provides you with tips on what to do with the people you identify as low performers.

Downloading this Identifying Performance Levels template can help you to assess each team member on each of the following criteria

• Technical Competence (capability to do the job)
• Quality of Work (standard of output)
• Performance Effectiveness (ability to meet targets and goals)
• Living The Values (interpersonal skills and personal style)