Task: Question Generation
Input (English): Passage: The Redskins primary weapon in the backfield was running back Earnest Byner, who ranked 5th in the NFL with 1,048 rushing yards, while also catching 34 passes for 308 yards and scoring 5 touchdowns. Rookie running back Ricky Ervins was also a major asset to the running attack, rushing 145 times for 680 yards for an average of 4.7 yards per carry, while also catching 16 passes for 181 yards. And when Washington was near the goal line, they usually relied on fullback Gerald Riggs, who rushed for 248 yards and scored 11 touchdowns. The Redskins offensive line, known as "The Hogs (American football)", was led by Pro Bowl tackle Jim Lachey and guard Mark Schlereth, along with four-time Pro Bowl veteran Russ Grimm. The Hogs allowed the fewest sacks in the league with just 9, 10 sacks less than the team that allowed the second-fewest. Even Washingtons special teams unit was a big threat. Running back Brian Mitchell (running back) led the NFL in punt return yards (600) and punt return touchdowns (2) with a 13.3 yards per return average, while also gaining 583 yards returning kickoffs.
Output (English): Which three running backs were assests to the Redskins?