Whisenhunt said that Smith's versatility and ability to work with a number of formations should make the Titans harder to beat next season.
"What I really liked about Giff was his versatility with the defensive line - he has done both 3-4 and 4-3, which means he is flexible enough to adapt and yet still get good production out of his players," he told the club's official website.
"I know from having to play against him two years ago what a difficult challenge it was facing that group and how well he handled them. So we are excited to get Giff here to work with our defensive line."
Smith was appointed to the role on Thursday.