Jack Sock and John Isner add a twist to a favorite warm-up.
Bryans endorsing Hyper-G string.
U.S. captain Kathy Rinaldi names new face to team for semifinal.
World No. 1 encouraged with progress from elbow injury after facing Federer.
World No. 25 aims to return in Madrid next month.
Wondrous one-handed backhand not included.
Roger Federer and Andy Murray played a few sets in Zurich for a good cause on Monday
