He's soft-spoken, almost shy, an unassuming young guy with a flat top and a smile.

Jonathan Grimes seems like an ideal candidate to hang out with your son or date your daughter.

Until, that is, he straps on his pads, fastens his chin strap and lowers his shoulder into the throat of an oncoming defender.

"You've got to get a little mean in football, you know," Grimes said. "It's a violent game, so if you're too nice out there, you might be taken advantage of. Everyone on the football team is good guys, but that nice stuff has to go when you step on the field."

Grimes, William and Mary's sophomore running back, leads the Colonial Athletic Association with 92.2 rushing and 140.8 all-purpose yards per game and is a big reason the fifth-ranked Tribe (9-1, 6-1 CAA) boasts the league's most productive offense (378.7 yards per game) going into Saturday's regular-season finale at fourth-ranked Richmond (9-1, 6-1).

"We talk about, within our position, playing a very physical game," William and Mary running backs coach David Corley said. "That's something we've really worked on here the last couple of years, is building that mentality. ... I can be your friend and I can shake your hand off the field, but when we get on the field, it's nothing personal against you, but I've got to get my job done and be a very physical force."

Grimes ranked 12th in the nation as a freshman with 162 all-purpose yards per game last season en route to earning CAA offensive rookie of the year honors. While that stat has dipped slightly this season, his presence may loom even larger, thanks to the stocked, healthy backfield the Tribe lacked in 2008.

With juniors Courtland Marriner (409 yards and a team-best seven rushing touchdowns) fully recovered from a knee injury and Terrence Riggins (221 yards) back from an ankle injury, the Tribe features a three-pronged attack that tests defenders' skill and focus.

"You can't just key on (Grimes)," Corley said. "You have to be aware of Marriner. You have to be aware of Riggins. … You don't have to put Jonathan at every single position to get the job done. You've got Courtland to go out on the perimeter and run routes, or Riggins, and leave Jonathan in the backfield, or you can put Jonathan out on the perimeter and let him run routes and let those other guys get carries. It allows you to be more multiple."

Grimes, who also has 34 catches for 181 yards and a TD, said he understands those offensive options better this season.

"I can see the big picture of what everyone's doing on the perimeter," Grimes said. "They put the running backs in all different kinds of spots, so our jobs might change. … Last year, I felt like I was just knowing my job, just doing my job. Now, I know how my job affects everyone else."

Grimes' game-day performance, which included a 54-yard burst in the Tribe's 20-17 victory against New Hampshire last weekend, isn't the only thing that has an impact on his teammates.

"He practices hard, doesn't say much, just kind of goes about his business, and just works really, really hard," William and Mary head coach Jimmye Laycock said. "I think he kind of brings the other guys along with him, too. They're either going to do it like him or they're going to get left way behind."

To transform from the understated piano player he is off the field to the tackler-shedding force he becomes on it, Grimes finds motivation in music and in film clips.

"I've been recently watching a lot of highlights by Adrian Peterson," Grimes said. "He runs very violent. … He has a mind-set when he runs, like 'You can't tackle me.' I remember someone asked him, 'Could someone tackle you one-and-one?' and he's like, 'If they get lucky.' That's his mind-set, and I just like that."

It's an approach William and Mary opponents are beginning to understand all too well, and that familiarity isn't through breeding contempt.

"We got Jonathan for two more years, and we've got Marriner and Riggins for one more year apiece," Corley said. " I think people probably will be thinking, 'Aren't these guys supposed to graduate at some point?' "