Minor League Baseball Relief Act This bill establishes a program for the relief of certain minor league baseball clubs and independent professional baseball clubs that experienced large business losses. The bill provides funding for the Small Business Administration to make grants to such clubs that experienced decreases in gross revenue in 2020 of at least 75%, as measured against revenues in 2019 (or, if revenues were negatively affected by a natural disaster or weather disruption in 2019, by the average of revenues over the prior three-year period). The source of funding for the grants shall be funds appropriated under enacted COVID-19 relief legislation that have not been obligated and are no longer being used to carry out activities authorized under those laws. Grant amounts provided to any club may not exceed $10 million.