The Bills hired Downing last week and Manuel, who has worked with the coach at last season's Senior Bowl, said that he would continue to learn a lot working closely with him.
"I'm very excited to work with coach Downing," Manuel told the club's official website. "I have a previous history with him last year at the Senior Bowl.
"I think he has a ton of talent and a lot of new edge to him as a coach. He's a young guy as well, so I'm looking forward to working with him.
"He kept in touch with me throughout the whole thing beyond the Senior Bowl. He checked in with me when I was going through the pre-draft process. When I saw him in the preseason last summer when we played Detroit we talked again and I'm excited he's on our staff."
Manuel was drafted by the Bills at the start of the 2013 season.