This is against the sportsmanship of the game and violates the fair play of yahoo leagues. However, there is no game mechanics that will force players to starts. The only way to prevent this would be the commissioner editing the rosters for the game. I would recommend him to start the highest projected for each team and let the cards fall where they do.
My guess is that you have a 5-7 records and the commish has a 6-6 record, in which case you are out of luck.