Predicted Winners in BOLD
 Marin Cilic (CRO) vs.  Jack Sock (USA) H2H – The winner of this match will keep his semifinal hopes realistically alive. Cilic has more experience and a more well rounded game. Jack Sock has his massive forehand and momentum from winning in Paris. Sock leads their head-to-head 2-0 with both wins coming in 2016 (Davis Cup and US Open). I think so long as Sock is not over-awed by being in the O2 at the World Tour Finals that Sock’s momentum from Paris will likely carry him to a 1-1 round robin record.
 Roger Federer (SUI) vs.  Alexander Zverev (GER) H2H – This should be the main event of the day and perhaps of the entire round robin. I think Federer’s slice backhand will help him keep the ball low often enough to eek out a win over Zverev. Zverev can certainly dominate Roger by overpowering him if Roger is not able to keep the ball out of his favored striking zones.