Jack Sock beat Denis Kudla 3-6, 6-2, 6-2 Sunday to win the U.S. Open boys' title in the first all-American junior final at Flushing Meadows in a decade. Top-seeded Daria Gavrilova beat Yulia Putintseva 6-3, 6-2 in an all-Russian girls' final. The 17-year-old Sock, a high school senior who grew up in Lincoln, Neb., is the first U.S. More...