Aaron Williams upset Bills haven't signed Fred Jackson

Fred Jackson is one of the most experienced running backs still available in free agency, and former teammate Aaron Williams thinks it's "ridiculous" his team hasn't signed the 35-year-old.

Williams and Jackson played together with the Buffalo Bills for four years between 2011 and 2014, before the running back played last season with the Seattle Seahawks.

Jackson was released by the Bills during training camp last season. He ranks third all-time in rushing yards for Buffalo with 5,646 yards in 106 games.

There have been no reports of contact between Jackson and the team.

The Bills' backfield is a tad crowded, but with power-runner Karlos Williams suspended for the first four games of the 2016 season, Jackson's services could be called upon.