Sumler plans to graduate in May and use his final season of eligibility at another school that might be in need of an experienced running back. Sumler will be able to play without sitting out a season if he is a graduate student at the school he transfers to.
Sumler leaves CU with career rushing totals of 714 yards and nine touchdowns on 199 carries, and 333 receiving yards and one TD on 45 catches.
In 2007, he recorded a career-high 100 carries, but that number fell to 36 last season.
Sumler told Buffs coach Dan Hawkins of his decision on Monday, according to CU.
Sumler is the second running back to leave the program since early November, following sophomore Darrell Scott. He is the ninth scholarship player to transfer from the program in the past calendar year.
Rodney Stewart, Brian Lockridge and Corey Nabors are the lone scholarship tailbacks left on the Buffs` roster.
CU coaches have only one commitment from a running back in the 2010 recruiting class. Adding another is now a priority with national signingday only three weeks away.
Size is now an issue as well in the Buffs` backfield. Current commitment, Tony Jones (5-foot-8, 185 pounds) is in the mold of Stewart and Lockridge, smaller but speedy.
If CU coaches are not able to add a bigger back to complement the rest of the group, coaches could ask junior Arthur Jaffee to switch back to offense after spending the 2009 season as a defensive back. However, there is no indication any move for Jaffee is currently being considered.
Jaffee, a product of Fairview High School and only a slight upgrade in size at 5-11, 205, is a walk-on who led the team in rushing in the three main spring scrimmages prior to the 2008 season.