In 1984, Ruthven began a downward slide in his effectiveness. He started the season as the opening day starter for the Cubs, winning on April 3 against the San Francisco Giants. Even though the Cubs would win the division with 96 victories, Ruthven would win only six games against ten losses, compiled in 23 games (22 starts). His earned run average also ballooned, rising to 5.04. It was his lowest win total since 1975. Ruthven did not appear in the 1984 National League Championship Series, which the Cubs lost in five games to the San Diego Padres.