This paper discusses a discounted Kelly criterion and its application to the Korean Professional Baseball League. As a result of the research, it is found that the time value of money does 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 considered in determining the optimal Kelly betting ratio. We present an example of the discounted Kelly criterion based on the Korean Professional Baseball Championship in 2004. Many of the results differ from those of the traditional approach.