Managers who practice favoritism in their employees are not professional, they are just experienced. They will never admit it, it will not be noticed sometimes, they will just try to justify their actions, and use their influences...
Favoritism can be either of the following:
1. Manager & Employee are beneficial to each.
2. Employee alone is benefited from the Manager.
3. Manager alone is benefited from the employee.

Favoritism can cause:
1. Rumors
2. Jealousy from other employees
3. Protest, confusion & distrust on the evaluation system.
4. Disturbance at work.
5. Opportunity for the favorite employee though constant anxiety & shame takes place.