How does the man feel about winning the race: "It's no _____ deal, honestly."?

The phrase "It's no big deal, honestly" is a common expression used to downplay the significance of something, in this case, winning the race. When someone says "no big deal," they imply that the event is not as important or impressive as it may seem to others. By choosing the term "big," the man is expressing a sense of modesty or indifference regarding his achievement, suggesting that he does not feel overly excited or proud about winning. This choice conveys a casual attitude, indicating that while winning a race may be an achievement, he does not see it as a monumental moment in his life.

In contrast, other options such as "small," "huge," and "medium" do not fit into the familiar idiomatic expression regarding the significance of an event. Specifically, "small deal" would shift the focus toward underestimating significance in a way that feels unnatural in this context, "huge deal" would have the opposite meaning, emphasizing importance rather than downplaying it, and "medium deal" is an awkward phrasing that does not effectively convey the intended sentiment. Hence, "big" seamlessly fits into the expression and accurately reflects the man's feelings about winning the race.