Casares was selected in the second round (eighteenth pick overall) of the
1954 NFL draft by the
Chicago Bears, but was offered a $20,000 annual contract with
Canadian Football League's
Toronto Argonauts. In the fourth game of the 1955 season, against the Baltimore Colts, he ran for an 81-yard touchdown. At the time, this was the second most yards gained in a single season in the NFL, short of the NFL single-season record by only 20 yards. During the following season, Casares again led the NFL with 204 rushing attempts, but his 700 yards was later eclipsed by
Jim Brown's 942 yards on two fewer carries. After ten seasons with Chicago, Casares was the Bears' all-time leading rusher with 1,386 carries, 5,657 yards, and forty-nine rushing
touchdowns. "He was the toughest guy I ever played with,"
Mike Ditka, a former Bears tight end and coach, told The Tampa Tribune. "I remember him playing on a broken ankle." Casares was questioned in 1962 by NFL investigators as part of a spreading inquiry that included the FBI into links between league players and organized crime. Casares, who had been seen with a bookie and was known to visit with other Bears players two nightclubs connected to the Chicago mob, said he had been questioned about point shaving for gamblers and had taken and passed two lie detector tests. The investigations eventually would lead to the one-season suspensions of
Alex Karras, of the Detroit Lions, and
Paul Hornung, of the Green Bay Packers. Casares finished his professional career with the NFL's Washington Redskins in , and in with the AFL's
Miami Dolphins, receiving only limited carries in his final two seasons. ==NFL career statistics==