TUCSON, Ariz. (AP) -- Ka'Deem Carey has always run with ferocity, bursting through the line of scrimmage like a bottle rocket, punishing defenders who would dare to try tackling him.
After a difficult offseason, he's running with even more of a chip on his shoulder this season and has barged into the Heisman Trophy conversation.
''I'm hungrier,'' Carey said. ''I have to be hungrier.''
After a solid freshman season, Carey had a breakout year in 2012, earning unanimous All-American honors after setting school records with 1,929 yards and 23 touchdowns, and leading the nation with 146 yards per game.
He set a Pac-12 record with 366 yards against Colorado and became the first player in the conference to rush for over 200 yards in consecutive games by running for 204 the next week against Utah.
Carey's accomplishments on the field were tarnished by what happened off it after the season ended.
In December, he was charged with misdemeanor assault and disorderly conduct stemming from a domestic violence accusation involving his then-pregnant girlfriend. Charges were dropped in June, but the stigma of the incident lingered.
Carey also was kicked out of an Arizona men's basketball game at the McKale Center after getting into an argument with a security official, during which he reportedly asked, ''Do you know who I am?''
Embarrassed by the blights on his character, Carey dedicated himself to getting better, put his work ethic into overdrive during spring practices, summer conditioning and the preseason, and entered the season with added bulk and an I'll-prove-you-wrong attitude.
Rodriguez opted to sit Carey for Arizona's first game for his off-the-field miscues and his star running back accepted the punishment without complaint.
''He's really responded well in the last six or seven months since there were some things in the (offseason),'' Rodriguez said. ''He's responded as well as we could have possibly hoped, and I'm really proud of the way he's focused. He comes to practice and works as hard as anyone we've got.''
Once Carey returned to the field, he became a wrecking ball who crashed the Heisman race.
The 5-foot-10, 207-pound back burst out of the gates in his first game against UNLV in September, taking his first touch 58 yards for a touchdown. He had 171 yards in that game and kept piling up the numbers, stretching his school-record streak of 100-yard rushing games to 12 by gaining 149 yards in the Wildcats' 31-26 loss at UCLA.
Carey is second nationally in rushing yards per game at 152.6 and is sixth in total yards rushing with 1,221 despite playing in just eight games while all the other leaders have played at least nine.
He is second on Arizona's all-time rushing list with 3,575 yards and appears to be a lock to better Trung Canidate's record, needing 249 yards entering Saturday's game against Washington State.
Carey was named one of 10 semifinalists for the Doak Walker Award on Thursday and has added his name to the short list in the Heisman race after being an afterthought at the start of the season.
''That's a goal you write since you were little,'' Carey said of winning the Heisman. ''That's a goal you just throw out there and hope you can catch. I'm going to keep chasing it. This team is going to keep chasing it.''
Carey has been a perfect fit for Rodriguez's up-tempo, spread offense, a versatile back with good vision, cutback ability and the speed to outrun defenders if he gets in the open field.
What sets Carey apart is his relentlessness.
Instead of easing into a hole or bracing to be tackled, he explodes into the line of scrimmage and initiates contact when he's about to be tackled. Every inch is like a fight for survival for Carey and those who try to tackle him often are the ones who pay the price.
''He is an incredible player,'' Colorado coach Mike MacIntyre said. ''Everyone knows about his ability to cut, but he is extremely tough and physical. When he doesn't have a place to go he tries to punish the guy trying to tackle him. If there is a better running back in America, I want to see him. He's the best I've seen in a long, long time.''
And he seems to keep getting better, thanks to that chip on his shoulder.