Which currently existing FBS and FCS rivalries are absolutely
essential to protect as annual matchups in any sort of realignment? This includes matchups that may end up as out-of-conference games.
Here is an attempt at a full listing of current "essential" rivalries among FBS schools. These have been continuously played for at least 30 years and are all listed on
Wikipedia. Excluded are longtime annual matchups which (to the best of my judgment) have continued mainly because the schools share a conference or division and not due to any particular rivalry (e.g., NC State/Wake Forest, played continuously since 1910). In parentheses is the first year of the active run of annual matchups for each pair.
Air Force/Army (1971)
Air Force/Navy (1972)
Air Force/Colorado State (1978)
Alabama/Auburn (1948)
Alabama/Tennessee (1944)
Arizona/Arizona State (1946)
Army/Navy (1930)
Auburn/Georgia (1944)
Bowling Green/Toledo (1948)
California/Stanford (1946)
California/UCLA (1933)
Central Michigan/Western Michigan (1973)
Cincinnati/Miami-OH (1945)
Clemson/Georgia Tech (1983)
Clemson/South Carolina (1909)
Colorado State/Wyoming (1946)
Duke/North Carolina (1922)
Florida/Florida State (1958)
Florida/Georgia (1944)
Florida State/Miami-FL (1969)
Georgia/Georgia Tech (1925)
Illinois/Northwestern (1927)
Indiana/Purdue (1920)
Iowa/Iowa State (1977)
Iowa/Minnesota (1931)
Kansas/Kansas State (1911)
Kentucky/Tennessee (1944)
LSU/Ole Miss (1945)
Miami-OH/Ohio (1945)
Michigan/Michigan State (1945)
Michigan/Ohio State (1918)
Minnesota/Wisconsin (1907)
Mississippi State/Ole Miss (1944)
Navy/Notre Dame (1927)
NC State/North Carolina (1953)
New Mexico/New Mexico State (1946)
North Carolina/Virginia (1919)
Notre Dame/USC (1946)
Oklahoma/Oklahoma State (1910)
Oklahoma/Texas (1929)
Oregon/Oregon State (1945)
Stanford/USC (1946)
Tennessee/Vanderbilt (1945)
UCLA/USC (1936)
Virginia/Virginia Tech (1970)
Washington/Washington State (1945)