FORT WORTH, Texas - If Jeff Robinson looks as if he hasn't slept, it's because he hasn't.

"I've had a sick feeling in my stomach for the last three weeks," said the reigning two-time Stock Contractor of the Year, who is feeling overwhelming anxiety and sorrow over what could well be the final outing for the legendary Chicken on a Chain.

This weekend's appearance in Greensboro, N.C., is rumored to be Chicken's final out.

Robinson said the once-in-a-lifetime bull is in good shape, however, and if he performs as well he has throughout his career, Chicken on a Chain could possibly compete one last time in Las Vegas at the World Finals.

"It's not totally out of the question," Robinson said.

Robinson purchased Chicken on a Chain in 2006. For much of their first year together, Chicken on a Chain was considered mean and hard to handle. Robinson considered selling him, in fact, but instead loaded him on his trailer and hauled him to one Touring Pro Division event after another for much of the year.

That was just start of what would soon become one of the most prolific and memorable careers.

In 2007, Chicken won the World Champion Bull and arguably became the most popular bucking bull in PBR history.

That year he bucked off a career-best 94.44 percent of the riders who drew him. Of his 18 outs, 12 were at the BFTS. He was ridden only once, when Justin McBride made the whistle for 93 points. His average bull score was 46.188 points, with an average mark of 23.2 points per judge.

He's had 125 career outs - 78 of which have been at the BFTS - and holds a career average of 45.02 points. His 78 outings at BFTS events are the most of any active bull, and eighth on the all-time list of outs. Probullstats.com, which has stats for 25,944 bulls, lists Chicken as the only bull with more than 100 PBR outs whose average score is 45 points or better.

He's fourth on the list of all-time 90-point ride producers, and of his 78 outs at the BFTS he's been the high-marked bull 41 times. Thirteen times riders have won a round on him.

Renato Nunes and Chicken on a Chain nabbed 11th on the all-time list of highest scores in PBR history in 2008, when they teamed for 95.75 points in the Championship Round at St. Louis. It's the third-highest score, behind scores of 96.5 and 96 points.

The 12-year-old bull is in his seventh season. To put that into perspective, in his first year on the BFTS he bucked off the likes of Cody Hart and Tater Porter.

Although every great athletic career comes to an end, Robinson said it's hard not to dread the finality of this coming weekend.

"It's hard to put in words, really," he said.

Thanks to Chicken's success, Jeff Robinson Bucking Bulls quickly went from hauling four or five bulls to 10 or 12. Two years after buying Chicken, he had 25 bulls and was capable of helping fill out the pen at both a BFTS and TPD event in the same weekend.

Last year, Robinson could haul a trailer load of short-round- and Championship-Round-caliber bulls to every BFTS event without hauling the same the load two weeks in a row.

Chicken's impact is comparable to what Ray Lewis has meant to the Baltimore Ravens, or athletes such as Albert Pujols and Shaquille O'Neil.

"You hear in sports where one guy carries a team," Robinson said. "Well, this bull carried me. He gave me the opportunity to be where I'm at. Without him I wouldn't be where I'm at, no doubt."

What has made Chicken on a Chain an undeniable fan favorite is his sheer size, along with his athleticism and proven track record for success. He moves every bit of the 2,100 pounds he's estimated to weigh.

Robinson said he's never seen a bull that size move as quick as Chicken on a Chain, which is likely what caught the hearts and imaginations of PBR fans around the world. To this day, he receives the loudest standing ovation upon his introduction.

Robinson said the pronounced and extended applause still gives him goose bumps today.

Although he hasn't gotten a full night's sleep in weeks, Robinson doesn't figure to get much this week either. In fact, he said, "I think Friday night will be one of the hardest nights I've ever had."

This past weekend, in Tampa, Fla., several bull riders talked about what they remember most about Chicken on a Chain and what separated him from other great bulls.

"You hear in sports where one guy carries a team. Well, this bull carried me. He gave me the opportunity to be where I'm at. Without him I wouldn't be where I'm at, no doubt."

BRENDON CLARK
"I remember seeing him at some Touring Pro (Division events), early on, and he was really wild. For a bull his size, super-athletic is the best way to explain him doing it at this level. That's amazing. He's a bull that went for a long time without getting ridden, and then some of the best rides I've seen have been from that bull. Justin McBride and Renato Nunes are two that come to mind. He was an exceptional bull."

KODY LOSTROH
"The thing I'll remember about Chicken on a Chain is that he brought it every time. He never had an off day, and he bucked for a long, long time. There's nothing you can take away from him. He'll go down as one of the best ones we've had. The thing about Chicken is he was big and strong and smart. I got on him three times and he got me on the ground every time."

AARON ROY
"That was one of the biggest bulls I'd ever been on. I watched him on all his outs and then whenever I got on him, he did something totally different with me. He went right with me and I wasn't expecting it, but, yeah, he was out of character. I thought I'd get along with him good, being he was a big bull. He was athletic for as big as he was. You expect big bulls like that to be slow and real heavy, and he wasn't. He was fast, could move in any direction he wanted to and in any amount of time. He was everything you look for in a bucking bull. He had the looks, big horns, he had the attitude and he bucked really hard. If you stayed on him, you were going to win the bull riding and if not, you were going to hit the dirt real fast."

ROBSON PALERMO
"I rode him, I think, two times and I have a couple scars. One under my chin and one on my head, and he did that. He's kind of a big bull, he bucks and he's a good bull to get on. His horns are really big. When you see him on the back of the chutes his body is little and he has big horns. When I got here I saw him on the Touring Pros, and I wanted to get on him because he was a good bull for me. He turned back to the left, but I never had a chance to get on him on the Touring Pro. When I saw him here on the Built Ford Tough (Series), he got so big and bucked all different. Now he's going to be retired."

BEN JONES
"You'd either be 90-plus on him or he'd throw your head hard into the ground. He was the perfect bucking bull, in my eyes. He wasn't a little muley. He was big and had two horns as big as baseball bats, so if you were going to get him rode you had to be a bull rider. You couldn't be half-hearted. He would give it his all, like we would give it our all, all the time. What I'll remember is Justin McBride on him. I still go home and watch that bull ride and visualize it. In my eyes it was the greatest bucking bull and the greatest bull rider there's ever been, and it was a clash of the titans."

AUSTIN MEIER
"Probably one of the things I'll remember most about him is my rookie year, going to the Finals. I had him in one of the middle rounds there and, you know, back then he was just a tall, slap-sided calf. He really bucked and I dang near got him rode, and a few months after that I saw him again when I had him drawn in a short round. He was this big solid bull that we know now. He frapted me harder than I've ever been frapted, and hooked me pretty good after that too. He was really, really strong; it was hard to find a nice seat on him. He had a lot of heart. Bulls like that, they like doing their job. He was good at doing his job and he stayed healthy. He had the health and he had the heart, and he just loved bucking."

J.B. MAUNEY
"When I first saw that bull he was probably the meanest bull I had ever seen. I hung up on him a few times and that got pretty scary. He's a big ol' bull and he's been great for a long time. There are not many bulls that can go that long, travel as many miles as he traveled and still be that good. He'll go down as being one of the best bulls ever. He had heart, plus he weighed about 2,000 pounds. He was huge, but he had heart and you could tell. He never missed a beat, but he might change something up - he'd go one way one week and then he'd go the other way. You never knew what he was going to do, but he always bucked."

Follow Keith Ryan Cartwright on Twitter @PBR_KRC.