Hookstratten arranged also for Allen to train with Olympic track and field coach Jim Bush, who also trained record-breaking Olympic sprinter Quincy Watts during his 20-year career at the University of California. The training program with Bush helped Allen to improve his endurance and strength as he entered his rookie year with the NFL. One week prior to the season opener against San Francisco Allen moved into the starting lineup. In that game he gained more than 100 yards rushing. A second game against Atlanta was followed by an eight-week (57-day) players' strike, the longest in NFL history.
The Raiders returned from the strike with a win in a Monday-night home game against the San Diego Chargers. When the shortened season had ended, Allen had rushed for 697 yards and 11 touchdowns. His 401 receptions that season included three touchdowns. At the Tampa Bay stadium for Super Bowl XVIII in 1984, Allen broke loose for a 74-yard touchdown run after the Raiders took possession of the ball on their own 26-yard line in the last 12 seconds of the third quarter. The score by Allen turned the tide for the Raiders, and the team won the Super Bowl for the third time in franchise history. He wrote of the experience later, "There are those moments in life that simply defy proper explanation, so magical that they beg a poet's talent for description. They pass all too soon, a blur in time so quickly gone that there is not ample opportunity to fully appreciate them as they occur. Such a moment for me began when [Jim] Plunkett called the play."
During the 1985 season, Allen injured his ankle at the home opener against the New York Giants. It was the team's third game—and their third straight loss. The injury—although nothing appeared broken—plagued Allen for some time. Although he was named to the Pro Bowl that year, the doctors refused to release him to play, and his stats sagged in 1986.
After a lackluster 1987 season, and another player's strike delay, Allen led the Raiders on the rebound in 1988, for the seventh time in his career. He re-signed with the Raiders in 1989 but played only sporadically through 1991. The 1992 football season marked Allen's eleventh and last with the Raiders. He signed with Kansas City and played out his career with the Chiefs until retiring from professional play in 1997.
When he retired after 221 games played, Allen had logged 145 career touchdowns including 123 rushing touchdowns. His NFL record of 11 consecutive games with 100 or more rushing yards stood from 1986 until 1997. Third in pass receptions, with 587, and seventh on the all-time rushing list with 12,243 career yards, he was a six-time Pro Bowler. His 1985 single season mark of 2,314 combined rushing and receiving yards is the third-highest in the NFL.
Allen, who married Kathryn Eickenstadt on June 26, 1993, lives in Montecito, California. In retirement he works as a sports analyst for the CBS television network's NFL broadcast team.