hmm.. i think what I'm trying to point out did not come across..,
Let's start with your query, you are asking is this
"Pls help us out identify all the unjust and unfair labor practices therein"
First, Labor and employment laws don't mandate performance appraisals. but they do prohibit discriminatory employment actions based on nonjob-related factor.
Second, what i was trying to state is performance appraisal or ratings is usually based on factuals and data. usually performance rating consist of many factors or what we called category.
for the premise that you are asking - the example stated previously is based on 2 categories we've used in manufacturing setting which is the most important for that industry - quality output and quantity output.
low quality output yields to rejections and increase cost. low quantity output leads to less stock and poor brand image because company cannot deliver. if an employee is required to hit production of 500 units per day, at 100% quality, he gets the full 5 points on each category. however if he only produces 250 units and some defects on the quality of the product, he gets 2.5 points on quantity output and 2.75 points for quality.
Now, back to the query, from the companies i known, there is no category or point system that will give additional points because the employee is injured, work related or other wise. but the company would take note in the Performance Appraisal that the output was affected because of the injury. Usually this will exempt the employee for any corrective actions because of poor performance at that time.
BTW, employees cannot be terminated due to 1 poor performance rating. it has to be many performance rating with no improvement after being given training or ways for the employees to improve.