The world No. 1 needs a break after winning his fourth US Open title and leading Serbia in Davis Cup.
Alejandro Davidovich Fokina has joined Team Europe.
Just 13 of the Top 30 are playing in the Mexican 1000.
The American says that Gauff has a runway for many major titles.
"Beyond belief," self-described "long-suffering" Jets fan John McEnroe said of Aaron Rodgers' season-ending injury.
On the day of his grandmother's funeral, Andy Murray delivered an emotional tribute.
"I need to listen to my body," four-time Grand Slam champion says in withdrawal.
