McClain and the running game will carry the Ravens' best opportunity to advance past Miami in the 1 p.m. AFC wild-card playoff. A victory at Dolphin Stadium would earn the sixth-seeded Ravens a date against the top-seeded Tennessee Titans in six days.
A grinding run offense has become an integral part of the Ravens' 11-5 success this season. They led the NFL with 592 rushing attempts in the regular season, 32 more than the team with the next biggest commitment to the run, the Atlanta Falcons.
Whether it's McClain, Willis McGahee or Ray Rice, the Ravens have moved the chains consistently on the ground. The team averaged 4.0 yards a carry in the regular season, and its 148.5 yards per game ranked fourth in the NFL.
Quarterback Joe Flacco feeds off the running game with play-action passes in an increasingly big-strike offense. Stopping those runs will be the top priority for the Dolphins' defense.
"That is their thing," linebacker Channing Crowder told Miami reporters last week. "They are a hard-nosed football team. They are going to bash you, run the ball, do play-action and try to get you to bite up on the run to throw the ball.
"They aren't going to sit back in five wides [spread offense] and throw the ball, because they don't have the personnel to do it. So if you can stop their run, you can pretty much control the game."
Miami could do neither Oct. 19 in South Florida, when the Ravens rushed for 140 yards in a 27-13 victory. The Dolphins believe the presence of veteran nose tackle Jason Ferguson, who missed the first game, will make a difference this time.
McClain, who has a fullback's body with a halfback's feet, disputes that notion.
"We know they're a different team from when we played them, and we're a different team," he said. "We've gotten a lot better every day since that Sunday. ... So if they're saying that getting one guy back is going to help them against the run, I don't think that's really going to help. They're going to need more than just one guy, because we're coming out and we want to run the ball."
McClain rushed only six times for 17 yards in Miami in Week 7. McGahee, a former Miami Hurricane, ran for 105 yards and a touchdown.
But McGahee has been inconsistent in playing time and production since then, while McClain has come on. McClain leads the team with 902 yards to McGahee's 671. Rice, a rookie who has missed the past three weeks with a lower leg contusion, has rushed for 454.
Confidence in the running game has grown proportionately with the team's success. Asked whether the Ravens believe they can run on any defense, coach John Harbaugh refrained from making a grand declaration.
"Well, you hate to make a statement like that, but I think there is a confidence," he said. "We think running the football is important to us. We have to run the ball well offensively to make everything work, and it's just something we believe in."
The Dolphins ranked 10th in the NFL in rush defense and last week expressed a confidence of their own.
"The running game is part of the main reason why Flacco has been successful," Miami linebacker Akin Ayodele said. "The offense is trying to emulate the defense and be physical. I know for us, I believe that we are built for a team like that and for an offense like that, and so we are looking forward to it."
A trip to Nashville hangs in the balance.
Baltimore Sun reporter Edward Lee contributed to this article.
RAVENS (11-5) @DOLPHINS (11-5)
AFC wild card; today, 1 p.m.
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Line: Ravens by 3 1/2