A majority of sports fans think that they could broadcast themselves talking about sports with friends and it could become successful. This is partially true but this is going to take hard work as well as constant consumption of sports related content. People might love listening to a podcast about football but a sports podcast has to include some other major sports. A fan could love your take on certain topics but simply not be interested in the main sport discussed. Do not alienate an entire demographic due to not liking a sport or refusing to watch it in order to give an educated opinion.
Covering hot topics in sports should be done as well but it is probably wise to avoid politics. This can lose a podcast listeners for life as many people feel very strongly about their political opposition. Gone are the days of people respecting that you have a different opinion so avoid this where possible. Sports has taken a much more political turn in certain leagues like the NFL with ratings going down due to people taking a stand on certain topics. Lastly you have to stick with your opinions on certain teams or subjects. People love to hate certain teams or support others so this can build a sense of personal rapport with listeners which is invaluable when growing a following.