Complex sentence: Dupree's 251-yard total NFL contribution volume yielded mild results in comparison to his previous professional football career in the United States Football League, or the 1393-yards gained as a college freshman at The University of Oklahoma.
Split into simpler sentences: Dupree's 251-yard total NFL contribution volume yielded mild results in comparison to his earlier professional football career in the United States Football League. It also paled in comparison to the 1393-yards gained as a college freshman at The University of Oklahoma.