A lot of schools have asked, "how can we get play-by-play for our broadcasts?" Having play-by-play commentary does add a level of professionalism to your production, however, it is not required. Utilize someone who's already calling the game - your PA Announcer!
Many schools have a designated PA Announcer for your field or gym, so use them to provide the audio during your productions. This requires splicing into the PA audio connection and then running that feed into the audio ports (red and white cables) into the video capture device. This technique is very simple and also allows you to cut down on your production staff.