"That's not the first time he's said that," coach Jeff Fisher said.
Mason was true to his word this time, breaking free again and again, fueling a highly unexpected laugher with three touchdowns.
"I told myself to achieve greatness," Mason said after the 52-0 rout over the hapless Oakland Raiders on Sunday. "I want to be the best player to ever touch a football."
Everything was ridiculously easy for the Rams, who have had their share of struggles. They just kept getting into the end zone.
"I'd have to think awful hard to come up with another game that kind of started off the way that one did," quarterback Shaun Hill said. "That was certainly fun."
Mason scored two long touchdowns and Hill accounted for three TDs in an out-of-nowhere 38-point first half that tied for second most in franchise history. The final margin was the second most for the Rams, topped only by a 59-0 victory over Atlanta in 1976.
The Rams (5-7) had zero hangover from a stinging three-point loss at San Diego last week. Hill was intercepted by Marcus Gilchrist at the goal line in the final minute of that defeat.
The Raiders (1-11) took their second-worst defeat in the franchise's 54-year history, falling just shy of a 55-0 whipping at the hands of the Houston Oilers in 1961 in the AFL. That was the Raiders' second season.
"It just wasn't us," quarterback Derek Carr said. "That didn't look like us. I don't know if flat is the word, but it just wasn't us."
In the first half, Mason had 113 yards rushing on six carries with an 89-yard score, plus a 35-yard jaunt on a screen pass that opened the scoring. Hill was 12 for 15 for 178 yards and two TDs and ran for a 2-yard score.
The Rams scored touchdowns on their first five possessions, then got a field goal on the sixth midway through the second quarter to top their previous-best scoring total for a game this season. The 38-point halftime lead was the largest in franchise history, one more than against Green Bay in 1980.
The Raiders had three extra days of rest after knocking off the Chiefs but were never competitive and committed five turnovers. Carr threw two interceptions leading to the Rams' final 10 points before halftime and was benched in the second half.
The shutout was the Rams' first since 2006, 20-0 at Oakland.
The Rams outgained the Raiders 203 yards to 34 in the first quarter. Oakland opened the game with three straight three-and-outs.
Raiders interim coach Tony Sparano said players weren't sharp in one practice this week, but added, "I didn't see this coming."
"This just got away from us," he added.
In a show of solidarity for protesters in nearby Ferguson, Mo., five St. Louis players stood with hands up before trotting onto the field during pregame introductions. Fisher said he'd not been aware the gesture had been planned.
After Mason scored on an 8-yard run in the fourth quarter, he and Britt raised their hands together.
"Everything about the situation touched me because it could have happened to any of us," said tight end Jared Cook, who joined wide receivers Kenny Britt, Tavon Austin, Stedman Bailey and Chris Givens in the pre-game gesture.
"Any of us are not far from the age of Michael Brown and it happened in our community. I wouldn't want to be in any one of those guys' situations that it happened to."
Additional security measures at the game included members of the National Guard toting firearms.
Rams G Rodger Saffold aggravated a nagging left shoulder injury in the second half and did not return, but expects to play next week at Washington. The Raiders voided a free agent deal with Saffold last winter because he failed a physical relating to the shoulder, and he quickly landed back in St. Louis. ... Raiders TE Brian Leonhardt (concussion) was hurt on a kickoff return in the first quarter and did not return. OT Menelik Watson (ankle) was sidelined in the second quarter. Sparano had no updates on either player. ... Fans in the north end zone held letters forming "Keep the Rams in St. Louis." The Rams' lease will be on a year-to-year basis after this season.