CHARLOTTE, N.C. (AP) — A person familiar with the negotiations says the Carolina Panthers have agreed to a four-year, $64 million contract extension with All-Pro running back Christian McCaffrey. McCaffrey’s $16-million-a-year deal surpasses Dallas’ Ezekiel Elliott’s as the richest ever for a running back. Elliott is making $15 million per season. McCaffrey ran for 1,387 yards and hauled in 1,005 yards receiving last season to join Marshall Faulk and Roger Craig as the only running backs in NFL history to reach 1,000 yards in both categories in the same season. The 23-year-old is the only player in NFL history with at least 2,500 yards receiving and rushing in his first three seasons.