|Not that this is any consolation, but research has found that recent performance, both positive and negative, tends to influence the ratings that managers give their employees. |
One way for managers to prevent this stilted outcome is to monitor employee performance throughout the evaluation period. By doing so, the manager has a clear and accurate overall picture of the work that the employee has been doing. With this approach, employee performance problems can be placed in a more equitable context. It sounds like your manager has not been doing this.
You can discuss your concern with your manager, but you should be certain that your performance during the rest of the evaluation period has as strong as you contend. If so, you should meet with your manager and indicate that you are confused over your ratings. Notice that you are expressing confusion rather than dissatisfaction. Provide your manager with factual data that demonstrate your successful productivity and attainment of goals, and then ask him or her to review your ratings with this additional information in mind.
Regardless of his or her reaction, it would probably be helpful to take this type of step before your manager rates you again, assuming that your performance is first-rate.