Is it time to let that under performing sales/recruiter go?

I heard a great interview this week between a local sports talk show "expert" and Cardinals manager, Tony La Russa.  The sport show expert had been pounding La Russa for the last couple of weeks about why he didn't bench Chris Dunkin because of poor numbers, and Juan Encarnacion, who has better numbers, now is sitting on the pine boards with a "sore" knee, after a number of questionable plays. 

The two prize fighters continued to circle each other and throw a few jabs but neither really landed to me.  THEN, it clicked what point Tony was trying to make with the interviewer that wasn't really interested in listen anyway.  Dunkin was more motivated to get himself out of the slump and Juan was just drifting along. 

Many things can affect a sales/recruiters performance that are beyond their control.  It's critical, as a manager, to have a good system that you REALLY KNOW, NOT THINK YOU KNOW, how hard they are trying before pulling the plug on a person's job.  Make sure you have good metrics that allow you to tear the job down to it's lowest level.  Judge on those.  The problem could be elsewhere or even in training.

Motivation should always be the key factor in hiring someone new and when letting someone go.  Of course, there are times when someone just isn't a good fit for the job, but those times should be obvious to the person and the manager, way before they are fired.