Otherwise, Ryan said he wouldn't have hired the 30-year-old woman to be the club's special teams quality control coach, making her the first full-time female assistant coach in NFL history.
Smith's hiring was announced Wednesday and was the main topic of interest when Ryan met with reporters on Friday.
"I hired Kathryn because I believe she is going to do a tremendous job," Ryan said. "I have been around her for seven years professionally, actually met her at an Eric Mangini camp many years before that.
"But I have known her professionally for seven years and the reason that I think she is going to do a tremendous job here, it starts with everything else just like any profession, you have got to have a work ethic, you got to have a passion for it, and I just like the way she is.
"She is really all about the team, how she can help and all that, regardless of the job we have asked her to do. She has done a tremendous job in that and exceed what we thought she would do."
Smith was an administrative assistant to Ryan prior to her promotion. She previously worked with Ryan when he was coach of the New York Jets and she followed him to Buffalo when he was hired by the Bills.
"I was surprised at first, but I also know Rex really puts a lot of faith in his staff and his people," Smith said earlier this week. "So from that standpoint it made sense knowing I've worked with Rex directly and indirectly for a number of years.
"So he knows my work ethic and what I've done in the past, but it was a bit surprising that he came to me with this."
Now the opportunity is there for Smith to make a mark.
"This is just another opportunity for her to move forward, you know is it an entry level position in the coaching field, it is," Ryan said. "A lot of people break in as quality control coaches, but don't think it is not an important position, because it really is. A very important position, but I feel great about it.
"I truly believe she is going to do a tremendous job this way. She does not have field experience per say, I get that there is no question about it, but I know she is going to excel in the other areas of being a quality control coach and I think she is going to be successful on the field as well."
Smith wasn't the only recent addition to the Bills' staff. Ryan also hired former Baltimore Ravens safety Ed Reed as assistant defensive backs coach and his brother, Rob, as assistant head coach/defense.
Ryan saw Reed's work ethic first-hand when he was running the Ravens' defense.
"Ed Reed is a young man who is going to be a first team Hall of Fame guy, I don't there is any doubt about that," Ryan said, "but what maybe we don't know is was the most instinctive player maybe that we have seen playing that safety position.
"Part of his things about being instinctive, and all that is true, is his preparation. I saw it in Baltimore for all those years I had Ed. He was really, you talk about a leader, he was such a leader. It was phenomenal."
"He is as much of a grinder as you will see," Rex Ryan said. "He loves the idea, preparation, he knows the value of preparation, and bringing that to this football team, and his expertise that is something I am really excited about.
"Obviously you know from a personal standpoint it is my twin brother and things, and I love having him in the building with the other guys."
Rex Ryan said Dennis Thurman will remain as defensive coordinator despite the presence of his brother, and the head coach added he will continue to call defensive plays.