Taking on his opening-round opponent Marcus Copil in Washington, D.C., Jack Sock was loose. He was so loose in fact, he pulled out an insane no-looking backhand underhand shot, but lost the point.

Jack Sock is making good on his ATP Finals debut. He vanquished world No. 3 Alexander Zverev 6-4, 1-6, 6-4 to clinch the second semifinal spot on Thursday. He's the first American to make it this ...