Preview: Rafael Nadal vs. Tomas Berdych in London

Rafael Nadal and Tomas Berdych face off in the final Group A match of the 2013 Barclays ATP World Tour Finals on Friday evening. Nadal is already guaranteed a spot in the semi-finals, while Berdych, along with Stanislas Wawrinka, have to win today in order to have a chance of advancing. Watch live matches at TennisTV.com