The aim of the research is to determine the structural and semantic peculiarities of idioms in modern English online sports discourse. The work is novel in that it is the first to identify the types of idioms in rugby match reports and to classify the main sematic fields they refer to. The paper considers the semantic peculiarities of idiomatic expressions and their role in the implementation of the main functions of a match report, i.e., the information function and the influencing function. The analysis allows the researcher to examine the communicative-pragmatic goals of using set expressions in sports discourse, as well as to determine the main types of idioms according to A. V. Kunin’s classification. It is revealed that the idioms types are represented by nominative and nominative-communicative. As a result, it has been found that the idioms can be grouped into the following semantic fields: “Success”, “Difficulty”, “Struggle”, “Support”. The majority of the idioms belong to the semantic fields “Advantage”, “Achievement”, “Leadership”. The research findings have shown that idioms in match reports help the authors to convey a dynamic sports event in an expressive and emotional way and to fulfill the function of influencing the reader.