The actor can currently be seen in Talaash opposite Aamir Khan and Kareena Kapoor.
He told Hindustan Times: "Talaash was my last multi-starrer. I have decided to only do solo-hero films from now on. No matter how good the supporting role is, I won't do it.
"All my upcoming films have me playing the lead. This is a crucial time for me. I have to be careful about my career choices. I don't want to get swayed by success and sign everything that comes my way."
Siddiqui added: "I believe in method acting, though it is mocked a bit in Bollywood. I like to get under the skin of the character and understand the mindset of the person I am portraying on-screen."
The star is known for his roles in ensemble dramas such as the critically-acclaimed Gangs of Wasseypur.
He also appeared in Kahaani which is considered to be an influence on Talaash.
Watch the trailer for Talaash below: