"I'm still dealing with a couple of things in my knee," Wimbledon finalist said.
Andy Murray has posted 10 consecutive grass-court wins.
"I think people in the industry... they see me as a piggy bank," Emma Raducanu told The Sunday Times.
The American threw a fastball for a strike on Wednesday in Arlington.
The former World No.12 will take the reigns as the event kicks off across four cities in September.
The highest-ranked Norwegian in history will once again feature for Team Europe.
UTS, which will come to California in July, will be held in Frankfurt after the US Open in September.
