[1] However, in the early part of 2015, Beltz was rehired as Kerber's coach after the German suffered from a series of poor results to start the season, including losing in the first round of the 2015 Australian Open and dropping out of the WTA's top 10 for the first time since 2012.

[2] Upon their reunion, Kerber rediscovered the form that catapulted her into the world's top 10, winning four titles but not being able to reach a Grand Slam quarter-final during the year.

[3] Beltz has been credited with helping Kerber win her first Grand Slam title at the 2016 Australian Open, where the German defeated defending champion and then-world number one Serena Williams in the final in three sets.

[4][5] Kerber subsequently won the Olympic Silver Medal and a second Grand Slam title at the US Open (displacing Williams as the world number one in the process);[6] in addition, she also finished runner-up at the WTA Finals and finished the year on top of the world rankings.

[7] On November 16, 2017, Kerber announced on Twitter that she has parted with Beltz, and has hired Wim Fissette as her coach.