Mohnish is said to have left the show due to health reasons. His exit from the show is centred around an accident, and the scene was shown Tuesday night.
The show, which went on air last October, is the Indian adaptation of popular Pakistani TV series "Dhoop Kinare". It is about love between two doctors with a wide age gap.
According to a source, there will be no change in the original story to suit Mohnish's exit and Sharad's entry in "Kuch Toh...", aired on Sony.
Sharad has already started shooting for the show.
Earlier, there was a buzz that Anuj Saxena would replace Mohnish, but the production company, Director's Kut, finalised Sharad for it. Even Cezanne Khan of "Kasautii Zindagii Kay" was approached for the role, but the deal didn't work out.