The opening day of Week 2 at Wimbledon is to tennis fans what a college bowl game day is to football fans: nonstop action, all day long. The round of 16 begins today, and all players, men and women, play today in hopes of advancing. Several top seeds have been upset already, including Rafael Nadal. But there’s plenty of action and excitement still to come – starting this morning in particular: among the opening matches covered live by ESPN this morning is the latest example of the sport’s most electrifying sibling rivalry: Serena Williams vs. Venus Williams, who first faced each other at Wimbledon 15 years ago, in the semifinals (pictured). Today, they start serving right at 8 a.m. ET, so tune in early.