Many top players, including Venus Williams and Simona Halep, have changed their coaching arrangements as they prepare for the 2019 season.
Nicolas Mahut and Pierre-Hugues Herbert of France beat Croatia’s Ivan Dodig and Mate Pavic in the doubles on Saturday in four sets.
A collision of scheduling and warring interests puts one of tennis’s oldest trophies in competition with rival events.
The 24-team ATP Cup will take place in January 2020, a week before the start of the Australian Open and only two months after the revamped Davis Cup tournament.
Radwanska, who reached the 2012 Wimbledon final and No. 2 in the rankings, the first Polish woman to reach a Grand Slam final in the Open era, won 20 WTA titles in her career.
While Bob was injured this season, his twin, Mike, won two Grand Slam titles in men’s doubles with Jack Sock and rose to No. 1 in the rankings.