Can refusing to renew contract trigger bias case?

Q. As a small college, we employ quite a few adjunct in­structors, especially for night classes. They work on a term-to-term contract for specific courses. One instructor got a very poor review and we’d like to ease him out. He’s making noises about age discrimination. If we don’t renew his contract but instead use a younger, fresh-out-of-grad-school instructor, could he have a case?