Sandifer was drafted by the Washington Redskins in the 1948 NFL Draft out of Louisiana State, and that same season he led the NFL with a then record 13 interceptions. Dick "Night Train" Lane's 14 interceptions in a season is the only time Sandifer's record was surpassed in NFL history. Sandifer's 13 interceptions remains the All-Time single season interception record for the Washington Redskins. He also is included in a group of NFL players who hold the record for most interceptions in a game, intercepting four passes against the Boston Yanks on Halloween 1948, returning two of them for touchdowns, a record that has never been broken. Sandifer also spent time on the offense during his career. He had 74 career carries for 247 yards and one touchdown, with his first two seasons with the Redskins and his 1951 season with the Eagles being where he had most of his use. He also had 30 receptions for 510 yards and 5 touchdowns. He also returned 72 punts for 767 yards (with a 10.7 yards per return). He finished in the top 10 of punt returns in the league three times, finishing 3rd in 1948 (20), 6th in 1949 (18), and 9th in 1950 (15). He also had 63 kickoffs for 1,367 yards (with a 21.7 yards per return) and one touchdown. He was first in kick return yards and kick returns in 1948 along with 1st in kick returns in 1949 and 2nd in kickoff returns. He also finished in the top 5 of all-purpose yards, finishing 3rd in 1948 with 1,340 and 4th the next year with 1,161. He had 23 career interceptions, with 13 being in his rookie season.