Marbury made All-State at Monongah High and his senior year he was named "Back of the Year," and prep All-American. He won four letters in football, four in track, and two in basketball. He also complied the highest number of points in the state track meet his senior year.

As a freshman at WVU, Marbury carried the ball 61 times for 308 yards and scored two touchdowns. However, he hurt his ankle that year but recovered—and then some—during the spring. As a sophomore, he was one of the outstanding runners in the nation. He was four yards short of breaking the sophomore record set by Garrett Ford in 1965, even though he missed three and one-half games. That year, he carried the ball 145 times for 890 yards and six touchdowns. He also set new rushing mark in a single game with 291 yards in three quarters against Temple. He was named ECAC All-Star team twice for an October 9 showing against William and Mary and October 23 for his play against Temple. Marbury also competed on WVU track's 440 yard relay team.