Stosur, 30, has dropped to No. 19 in the rankings and is on her third coach in a year, having stopped working with long-time coach David Taylor before the 2013 U.S. Open. She then took on Miles Maclagan in November, but was back on her own at Wimbledon, despite having her best showing of the season by reaching the fourth round of the French Open.
The Australian fell in the first round of singles at Wimbledon, but won the mixed doubles with Nenad Zimonjic.
Meanwhile, Rea stopped working with Kyrgios following the teenager's first Grand Slam quarterfinal at Wimbledon, something the two had agreed on at the French Open.
The two have begun training together ahead of the hard-court season.