Trending @Wipro; Project delimma.

Hi Guys, I'm in a delimma to choose to stay or leave the project. Recently one of my senior collegue has resigned and actually he was main part of our project. Without him the project may get collapse. We are left one senior and after her it's me who is just 3 years old total experience guy. My manager spoken to me that the senior collegue is leaving so you have to take his place. And he is talking about Band progression as well. I'm not in a place take that much pressure and loose my mental peace. With just total of 3 years experience and replacing a guy who is 8+ years of experience. I know the expectation is high thats what killing me at the moment. I'm praying everyday so that senior take back his papers. Can anyone have gone through this and how did you face this?? How to be courageous in these times? Or is it better to resign? Please suggest...