Dennis, 27, actually finished three matches during the day, completing his third-round comeback with a 1-up victory over Mark Thompson in the morning after the match was suspended due to darkness Tuesday.
The Birmingham, Ala., native then defeated quarterfinal opponent Richie Taylor, 2 and 1, to advance to the semifinal round. His next victory came against USGA first-timer William Johnson, a 2-up win that secured his meeting with Eaton in the 36-hole match play final Thursday.
The 35-year-old Eaton, of New London, New Hampshire, used a 2-and-1 morning victory over Jeffrey Wilson to move into the semifinals, where he defeated Wright Waddell, 4 and 3. Eaton was previously a quarterfinalist at the 2002 Mid-Amateur.
The U.S. Mid-Amateur is one of 13 national championships conducted annually by the United States Golf Association, 10 of which are strictly for amateurs.