As an employer I have seen my employees have good days and bad. Sometimes those bad days seem to linger and start to consume their job performance. When you have a great employee whose work performance has been outstanding then notice a change you might ask yourself if there is something there worth saving. If so, maybe a quiet lunch together to see if they will open up and crack the door to working it out. If not, then maybe you should think about hiring a consultant to come in and help work it out. If there is something there worth saving it is in the best interest of both employer and employee to try and get to the bottom of the issue and a valuable solution.
Have a blessed day,