ST. LOUIS -- Let there be no lingering doubt: Tre Mason is the St. Louis Rams' starting running back and primary ball carrier.

If that wasn't already evident before the Rams' 22-7 victory against the Denver Broncos on Sunday, it should be plenty clear in the aftermath. Against the league's best run defense both in terms of yards allowed per game (67) and yards allowed per carry (3.19), Mason registered the first 100-yard game of his career and the most rushing yards against Denver this season. He finished with 113 yards on 29 carries, a middling but deceptive average of 3.9 yards per attempt.

“That’s how you have to beat this team,” Rams coach Jeff Fisher said.

While that average won't blow anyone away, the fact that Mason even got to 29 carries is a feat in and of itself. The Broncos had faced the fewest rushing attempts in the league this year, in no small part because they often shut down the run early and jump out to big leads.

But Mason was effective enough early on that the offense was able to move the ball and keep Broncos quarterback Peyton Manning on the sideline. Although the Rams defense was doing just fine on its own, it's a widely accepted theory that the best defense against Manning is often a good offense, especially one that can run the ball consistently.

"You have got to have that mindset, got to get first downs, got to stay on the field," Mason said. "I was doing everything in my power to keep us on the field."

Mason and the Rams did just that, controlling the battle in time of possession by keeping the ball for 35 minutes and 50 seconds to Denver's 24:10. They had 16 first downs and rushed for 131 yards on 33 carries as a team, their best output of the season on the ground.

And while Mason spent plenty of time hammering away between the tackles, he was also also able to shake loose for a big gain every once in a while. His 27-yard run was his fourth 20-plus-yard carry of the season; he remains the only Ram to do that this season.

Clearly, the Rams trust Mason enough to turn the game over to him, too. His 29 carries were the most by a Ram this season by 10. Even if many of those runs didn't get very far, Mason's performance was instrumental in taking the Rams to an unexpected victory.

"That’s just the way football is," Mason said. "Sometimes you have got to grind them out. It might not be a big play every play, but you’ve got to grind them out sometimes. That extra 1 or 2 [yards] means a lot when you’re on the goal line, so if you’re on the goal line, it can be the difference between a score and a first down."