The US Open tennis semifinals are underway. As Russian phenom Sergei Sergeyev and American superstar Tim Porter do battle under the lights on center court, Galina and Mallory, the funny and complicated women who share their lives, watch anxiously from the sidelines. But as the back-and-forth action unfolds, we journey into the minds of the players and the lives of the two couples in a fast-paced and moving exploration of family, parenthood, and the legacy we leave behind. Before it’s game, set, and match, more than a championship will be won or lost. Developed in the Globe’s 2014 New Voices Festival, Anna Ziegler’s energetic new play is a funny and visceral look at the sacrifices we make to stay on top.