A premier guard, Sweeney was versatile enough to fill virtually any offensive line position. He was named to All-Star teams and Pro Bowls for nine consecutive years at offensive guard, beginning with the 1964 AFL All-Star Team, and in 1970 was selected to the All-Time All-AFL second team. Sweeney spent 11 seasons as an offensive guard with the Chargers, then played two seasons with the Washington Redskins.
Sweeney, who stood 6'4" and weighed 256 pounds, was such an intimidating presence on the field that Merlin Olsen famously remarked he'd "rather sell used cars" than play against Sweeney each game. Sweeney was among several Chargers fined by the league in 1974 for drug use. A fierce critic of the NFL, he blamed the league for his prolonged problems with drugs and alcohol. Towards the end of his life he retained this bitterness. "If a guy breaks his back in the N.F.L., they'll pay him. That didn't happen to me. Instead, these guys broke my mind." He briefly served as a drug counselor at a San Diego hospital and appeared with Nancy Reagan in a promo for her "Just Say No" campaign.