Roger Federer will not return from a knee injury until the new year, having pulled out of the International Premier Tennis League (IPTL) because of "uncertainties" surrounding the event.
The 35-year-old Swiss has not played since a Wimbledon semi-final defeat by Milos Raonic in late July.
World number two Serena Williams has also withdrawn from the IPTL.
This year's tournament features one fewer team than last year, and has been undermined by financial difficulties.
Federer, a 17-time Grand Slam champion, is expected to be fit for January's Australian Open.
"We have had challenges this year, and we were hoping to get past them," said IPTL founder Mahesh Bhupathi.