For starters, they don't look anything alike. McFadden is tall, standing 6-foot-2 with skinny legs and tipping the scales at just 212 pounds. Hill, meanwhile, is short and compact at 5-foot-11 and 242 pounds -- give or take a few servings of food.
Their running styles are just as different. While both tailbacks are powerful enough to break tackles, McFadden has a tendency to run past defenders instead of barreling over them like Hill.
"Me and him, it's almost like two different ball games," McFadden said. "He's more of a power runner and things like that. I try to run with power but I have more speed than he does."
But for as many differences as McFadden and Hill have, they have each put up similar numbers for their respective teams this season.
McFadden, undeniably Arkansas' offensive leader, has rushed for 1,558 yards and 14 touchdowns on 265 carries. Hill, who hasn't gotten nearly as much attention in his first season as Wisconsin's starting running back, has gained 1,533 yards and 15 touchdowns on 292 carries.
As a result, today's Capital One Bowl is being billed largely as a showdown between two of the nation's top running backs. McFadden led the Southeastern Conference in rushing; Hill did so in the Big Ten.
Maybe they're not so different after all.
"They're both different body types, that's for sure," Wisconsin coach Bret Bielema said. "But they've both been productive.
"I did see a little feature (the other day) on ESPN, they were comparing the two on who they would take. One commentator said on third-and-8 he'd take McFadden, on third-and-1 he'd take P.J. So hopefully, we're in more third-and-1s than third-and-8s."
Both Arkansas and Wisconsin have offenses that are based on running the football and letting their big offensive linemen clear the way for their star tailbacks. But between the two running backs, McFadden would get top billing.
Hampered by a serious toe injury at the start of the season, the Little Rock native helped put the Razorbacks on a national stage by becoming the first player in school history to be named a Heisman Trophy finalist.
McFadden won the SEC rushing title by 559 yards, and his versatility while lining up at quarterback has made him even tougher for opposing defenses to stop.
"When I sat down and watched the Heisman Trophy presentation, I just saw some of his stats and really just kind of looked at it from a fan's perspective," Arkansas center Jonathan Luigs said. "He kind of turned some heads out there.
"... I'll take him over anybody in the country."
McFadden won the Doak Walker Award as the nation's best running back, but Hill made enough of an impression to be named a semifinalist for the award as only a redshirt freshman.
Hill is a running back in the same mold as former Wisconsin standout Ron Dayne, who won the Heisman in 1999. He's big and powerful with misleading speed and a knack for picking up yards after getting hit.
Hill is just the third Wisconsin freshman to rush for 1,000 yards in a season, and 249 of those yards came in a 41-9 rout of Northwestern on Oct. 7. The redshirt freshman plays tough, which is what one would expect from a New Yorker like Hill.
"He's not scared of anything. He'll go run up in the hole, run people over," Wisconsin quarterback John Stocco said. "Seeing that attitude in him and watching him run guys over kind of gets us up on offense."
Off the field, McFadden and Hill are known for being jokesters. And there are more similarities between the two tailbacks who seem so different.
When it comes to yards per carry, their averages are nearly identical. McFadden has a slight edge at 5.9 ypc to Hill's 5.2.
Both running backs also have been bothered recently by injuries that could affect their production in the Capital One Bowl. McFadden hasn't been at full strength since suffering a high ankle sprain and a strained Achilles tendon in a 38-28 loss to No. 2 Florida in the SEC Championship Game on Dec. 2.
Hill, meanwhile, has experienced discomfort in his neck and back.
But perhaps the biggest similarity between them is McFadden and Hill aren't exactly what they seem to be. Hill is surprisingly fast for his size, and McFadden is unusually powerful for his height.
"He's a big back, and I think what it is, you don't think he's fast but he's actually very fast," Arkansas defensive line coach Tracy Rocker said of Hill. "And that's the key to him. He's a big back, and he looks like a fullback but he runs like a tailback."
And what about McFadden?
"The thing about McFadden that jumps out to you is, everybody knows his speed but he's got great size," Bielema said. "He can run you over. I've seen him be very powerful, breaking arm tackles."
But while much of the focus will be on the running backs, McFadden doesn't see today's game as a heavyweight fight between two top running backs.
"It's not a challenge for me because I'm an offensive player; he's an offensive player," McFadden said. "So it can't be a challenge to me.
"I'm just going out there and playing ball."
McFadden and Hill: Similar Or Different?
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