How can a leader judge which staff member contributes least?

How can a leader judge which member of a team is least useful?

Use measures of each person's contribution. If several people have the same strengths and weaknesses, their roles may be duplicating one another.

A leader needs a sound basis for judging staff contributions. Performance measures can help identify what each person supplies to the organisation. When several people share the same strengths and weaknesses, their contributions can duplicate one another. The choice between them then matters less to the range of abilities available.