Source: RB William Stanback failed multiple marijuana tests at UCF

ORLANDO, Fla. -- UCF junior running back William Stanback, an All-AAC selection last season, has been dismissed for a continuous failure to comply with athletic policy and team rules, coach George O'Leary said Tuesday.

UCF did not cite a specific violation, but a source told ESPN's Joe Schad that Stanback had failed multiple marijuana tests.

Stanback told ESPN that coaches said he had a "bad attitude" after returning from an injury. He had appeared in two of the Knights' three games this season, rushing 12 times for 11 yards.

A projected starter in the preseason, Stanback came off the bench in UCF's season-opening loss to Florida International and played sparingly in Week 2 at Stanford. He did not play in last week's loss to Furman, as Dontravious Wilson, Taj McGowan and C.J. Jones have all taken the majority of the carries.

A year ago, Stanbeck earned all-conference honors after rushing for 697 yards and 10 touchdowns on 189 carries. He also rushed for 443 yards and six more TDs as a freshman in 2013.

Stanback told ESPN that he is likely to transfer, sit out next season and play as a redshirt senior. He also said he's been prohibited by UCF from transferring to FIU, FAU, Georgia Tech, Michigan, Maryland, Stanford, BYU and Texas.

UCF (0-3) travels to South Carolina on Saturday.

ESPN's Joe Schad and The Associated Press contributed to this report.