Bull was selected in the
1962 American Football League draft by the
Dallas Texans with the team's first pick, third overall. Bull also was selected by the
Chicago Bears as the seventh pick in the first round in the
1962 NFL draft. He ultimately signed to play for the Bears. There was a controversy over whether Bull already had signed a contract to play for Bears before the Gotham Bowl, which would have made him ineligible for that game. The Bears personnel director attending the game, future
Pro Football Hall of Fame coach
George Allen, denied that Bull had already signed with the Bears. After the game, Allen took Bull and his wife to Chicago, as part of the team's effort to sign Bull, before
Lamar Hunt, owner of the Dallas Texans, could sign Bull to play for the Texans in the
American Football League. Bull did not sign in Chicago and he and his wife went home to Texas. Allen pursued Bull across the country to preempt Bull meeting with Lamar Hunt in Texas. Allen spent five hours talking to Bull at
Love Field airport in Dallas, where Bull finally signed a contract with the Bears. Even without Allen's pursuit, Bull had reasoned that his best opportunity to play running back would come with the Bears. Bull was on the
1963 Bears world championship team. He was second on the team in rushing attempts and total rushing yards. When future Hall of Fame halfback
Gale Sayers joined the Bears in 1965, he became the focus of the run offense, and Bull played more fullback than halfback. When Sayers was injured nine games into the 1968 season, Bull stepped up and had his best rushing season with 472 yards and a 4.4 yards per carry average, and most rushing attempts since 1963. During his career, Bull played in 123 games, carried the ball 881 times for 3,222 yards and scored nine rushing touchdowns. He also caught 172 passes for 1,479 yards and five touchdowns. In a 1963 interview with
Sports Illustrated, Bull described the routine nature of the game's brutality. In only his third professional game, he took a fist to the chin while coming out of the backfield for a pass on a "sky pattern", and barely made it to the sideline before passing out unconscious. Bull had been forewarned that a back running a sky pattern had to anticipate being "clotheslined" by a defender. Two days later, his teammates laughed as they repeatedly watched the film of Bull being clotheslined. He described instances when he would be repeatedly kicked at the bottom of a pileup, have his legs intentionally twisted, received thumb jabs to the eyes, be bitten, and have one player drop an elbow down on his back while being tackled by another. Bull did not let his anger get the best of him in response, or let these events get under his skin, because it was "'all part of the game'", "'a matter of dollars and cents'". ==NFL career statistics==