Grand Slam kings will square off in an exhibition event in Saudi Arabia in October.
The German says he can't give the young talent what he needs right now.
Witt says he was surprised to find out from Pegula that she would be going in another direction.
The talented Kazakh rises to No.23 after taking home the Montpellier title.
The 34-year-old's long journey has finally taken her to the Top 100.
The Russian will not defend his title at the 500-level event.
"Sooner or later he had to lose, we were all aware of that. It's just a shame that it happened this way," coach Goran Ivanisevic said of world No. 1.
