Odd casting shuffling seems the order of the day. Just when we were getting over Tabu being replaced by Mallika Sherawat in Sanjay Chhel's film Maan Gaye Mughal-e-Azam we now have Suniel Shetty being replaced by Sonu Sood in Anees Bazmi's Singh Is Kinng.

Explains producer Vipul Shah, "Suniel had a serious dates problem. He's busy producing Mission Istanbul and the dates of my film were clashing with his. Being a producer myself now I know how difficult it is to orchestrate a film as big as Mission Istanbul. I’ll work with him in my next film. But this time he's required more urgently for his own film."

Suniel also goes with the dates theory but expands on the reason for his opting out. "Earlier the role had a lot of action in it. And that excited me. Now the role is very different." Interestingly, Akshay Kumar would be doing a lot of intricate fight sequences in Singh Is Kinng.

It isn't clear why the role offered to Suniel changed hues. But here's an intelligent guess.
One action hero in one film is enough.