This paper discusses a discounted Kelly criterion and its application to the KoreanProfessional Baseball League. As a result of the research, it is found that the time value of moneydoes not significantly affect the expected exponential growth rate when the time horizon is short,e.g., one month or less. However, when the horizon is long, the time value should be consideredin determining the optimal Kelly betting ratio. We present an example of the discounted Kellycriterion based on the Korean Professional Baseball Championship in 2004. Many of the resultsdiffer from those of the traditional approach.