The U.S. Open is moving its mixed doubles championship to the week before the tournament begins, hoping a revamped format and $1 million prize will persuade top singles players to chase a Grand Slam doubles title. This year’s event will feature 16 teams competing over two days in shorter matches. “What I would say is the reason behind this is to appeal to more fans and grow the fan base around the world,” said Lew Sherr, executive director and CEO of the U.S. Tennis Association.