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Sidney Thornton, a valued member of two Super Bowl-winning teams for the Steelers, has passed away, the team announced on Wednesday night. Thornton was 68 years old. 

Selected by the Steelers in the second round of the 1977 NFL Draft, Thornton was brought to Pittsburgh to help complement veteran running backs Franco Harris and Rocky Bleier. Thornton thrived in that role while helping the Steelers win their third Super Bowl of the decade at the end of the 1978 season. 

With Harris dealing with an early season injury, Thornton enjoyed an increased role in the Steelers' offense in 1979. He set career-highs in rushing yards and touchdown runs while averaging 5 yards-per-carry. Thronton scored 10 total touchdowns that season while helping the Steelers win a sixth consecutive division title. 

Against Miami in the divisional round, Thornton gained 86 total yards while scoring his first career postseason touchdown. He caught a 22-yard pass in Super Bowl XIV as the Steelers defeated the Rams to capture the franchise's fourth Lombardi Trophy. 

A physical back, Thornton played his entire six-year career with the Steelers. He scored 25 touchdowns (including the postseason) over that span while averaging 4.2 yards-per-carry. 

A New Orleans native, Thornton played college football at Northwestern State, where in 1986 he was inducted into the school's Hall of Fame.