Rihanna is no Mariah Carey but lets not pretend that the girl can't sing. She has a very unique and unpolished sound to her voice that alot of people admire. Not every artist is going to be Whitney Houston, they don't need to be. It's not so much about what tools you have, but how you use them. Jhene is no vocalist but she uses her voice well to create good music. Same with Rihanna. She can no doubt deliver this Sunday if she's been rehearsing

https://www.youtube.com/watch?v=6ZLa5IdJdU4