Dunlap played for the Pittsburgh Alleghenys from 1888 to 1890, and served as manager of the Alleghenys for a portion of the 1889 season. During his three years in Pittsburgh, Dunlap's offensive performance declined. His batting average for the Alleghenys went from .262 in 1888 to .235 in 1889. At the same time, he remained one of the leading defensive second basemen in the game. In 1888, Dunlap ranked second among the league's second basemen in fielding percentage (.940) and range factor (6.33), and in 1889, Dunlap's last full season in the major leagues, his .950 fielding percentage led the National League and was a career high for Dunlap.