Winston was promoted thrice in the very first year of his service. his managers stated that he was the "fastest worker they have ever managed" and that the quality of his work was "second to none." in the context of scientific management, winston is a(n)

Rate buster      

Explanation: Rate buster are those employees in the organization that manage to perform exceptionally and tend to give more output rate as compared with excepted rate.

They helps in increasing the productivity of the business speedily. Usually other employees dislike rate buster as they are also expected to perform with same rate as rate buster.

The statement mentioned in the question also states that Winston is a rate buster as he has got promotion thrice in a year due to his speedy , quality and exceptional work.