If you select the game on byutv's home page it is the link to watch LIVE TV, which you cannot rewind. If you go to the webpage that is specific to the game, however, you can rewind it as much as you'd like. Instead of selecting the link on the main page, go to shows, then sports, then Basketball (M). Select the BYU vs Utah St game from the recent games section. You should be able to rewind the game after starting it that way. Keep in mind it will initially start live, so I usually cover up most the screen with my hand and click on the left side of the scroll bar at the bottom of the screen right away so I don't see the score (I think the score is in the bottom right).

Disclaimer: This has worked for nearly every game this season for me since I never start it live, but it did not work for the UMASS football game since we didn't have rebroadcast rights and I also got an error when I tried it for the most recent basketball game and I got frustrated and went to watch it live since it was only 15 minutes in.