If your objective is to Maintain Salesforce Effectiveness, a solid indicator might be revenue per sales rep. If our revenue per sales rep is declining, it should be treated as a trigger for a broader discussion on the objective, not necessarily the KPI. At the same time, we will want to analyze a number of other performance indicators for a deeper, richer discussion.
When we look at KRIs for example employee turnover is this not just a performance measure against the objective Retain Great Employees?
In the end though, we are just splitting hairs by calling something a KPI or KRI. It matters far more that we have the discussion about the objective(s), than trying to build seperate processes to measure subtle nuiances.