Hill is an undrafted rookie who had 2,357 yards rushing and 11 touchdowns in 42 games at Eastern Michigan. The Bills released defensive end Erik Williams to make room for the signing announced Thursday.
Hill was added to spread out the load of carries during training camp. Dixon is expected to miss at least a month after he was hurt Monday.
Starter LeSean McCoy had a sore toe that limited him to individual drills for two days before returning to full practice Thursday.
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