It started with eight great football minds and seemingly a simple request.
Rank the 10 best running backs in NFL history.
By the time all was said and done, Don Shula, Marv Levy, Dan Reeves, Robert Smith, Jerry Richardson, Floyd Reese, Jack Bushofsky and Emmitt Thomas had thrown around nearly four dozen names, debated the merits of runners who had seemed flawless when they entered the Pro Football Hall of Fame and helped pare a list to include only the most elite of the elite.
(Click here for bios of panelists.)
With lots of input from those eight, ESPN.com subjectively developed a list that spanned different eras, took changes in the game into account and came to this conclusion -- Jim Brown was the best running back ever.
"I came into the league in 1965, and that was Jim Brown's last year," said Reeves, who played for the Dallas Cowboys before going on to coach the Denver Broncos, New York Giants and Atlanta Falcons. "There hasn't been anyone quite like him since, and I don't know that there ever will be. He had the size to run over people and the speed and elusiveness to make them miss. Nobody has ever had that combination quite like him."
Richardson, the first former player since George Halas to own a team when he was awarded the expansion Carolina Panthers, watched Brown from the sidelines.
"Everyone knows Jim Brown was great," said Richardson, who played receiver for the Baltimore Colts in 1959 and 1960. "But unless you saw it up close, I don't think you can truly appreciate the combination of power, speed and agility he possessed."
At a position that players with all sorts of different styles have had enormous success, Brown is the prototype of all prototypes. That's why he was the relatively easy choice for No. 1. At 6-foot-2 and 232 pounds, Brown played for the Cleveland Browns from 1957 to 1965.
Brown owned the NFL career rushing record with 12,312 yards when he suddenly walked away from the game to pursue a movie career. That record has been passed to Payton and now Emmitt Smith, but Brown's status has endured.
"There are a lot of ways you can look at the numbers," said Bushofsky, who worked in scouting and personnel for Tampa Bay, Indianapolis, Carolina and Washington for four decades. "But I think when you're talking about the best ever, you have to boil it down to how many times they touched the ball, rushing and receiving, and how many times they scored. You can't argue with Jim Brown on that."
In 118 career regular-season games, Brown scored 126 touchdowns (106 rushing, 20 receiving) while carrying 2,359 times and catching 262 passes. He scored once every 20.7 times he touched the ball, and he averaged 5.2 yards a carry and 104.3 rushing yards a game.
Reeves, Bushofsky, Thomas and Richardson each voted Brown first on their ballots. Shula split his first-place vote between Brown and Sanders, who finished No. 2. No panelist rated Brown lower than third.
"The only reason I'm not putting him No. 1 is because of his size," former Minnesota Vikings running back Robert Smith said. Smith rated Brown No. 2 behind Sanders. "He was running against defensive linemen who were the same size as him. That would be like a running back today running against 11 defensive backs. But that's not Jim Brown's fault."
Each panelist was asked to take into account the changes in the game. For example, Brown began his career when the NFL played a 12-game regular season. The league switched to a 14-game format in 1961 and to the current 16-game schedule in 1978.
Each submitted a ballot and agreed to make his top choice public, though some asked that the order of the rest of their lists be kept private. Each also talked extensively about the running backs on his list and, in many cases, about the players left off his list.
The ballots were calculated, but the result of the vote was used only as a guideline as ESPN.com assembled the final list. In some cases, less weight was given to votes from those who played with or coached a player, whereas more weight was given to impartial votes.
When it came to statistics, panelists were asked to try to think in relative terms. Players such as Brown didn't have as many opportunities to assemble as gaudy statistics as Tomlinson, who is ranked No. 6 and is the only active player on the list.
"To narrow it down to just 10 is nearly impossible," Reeves said. "I'm sitting here with a list of 40 or 50 guys, and you could make a legitimate case for every single one. You have to take in a lot of different factors and try to balance it all out."
Balance was what ESPN.com sought most as it tried to put every candidate into perspective. Panelists such as Levy, 82, and Shula, Richardson and Bushofsky, who are in their 70s, were relied upon heavily to present the case for the running backs some of the younger panelists never saw play.
Old-timers such as Red Grange, Marion Motley, Paul Hornung and Joe Perry received votes, but Brown and Moore (No. 9) were the only running backs who began their careers before 1965 to make the list.
"A lot of people forget about Lenny Moore or don't even know about him," Bushofsky said. "But he could stand the test of time. He was basically Marshall Faulk before Marshall Faulk."
Moore played for the Baltimore Colts from 1956 to 1967. He never came close to rushing for 1,000 yards in a season, but he was a combination halfback/flanker who produced 12,451 total yards and 113 touchdowns. Moore helped clear the way for running backs such as Faulk and Tomlinson to become huge parts of the passing game. Moore also played for, arguably, some of the best teams in history, and he helped his case by helping Johnny Unitas become one of the best quarterbacks ever.
Emmitt Smith: Big on results, not flash
Playing on a team that was a big winner wasn't necessarily a requirement to make the list. Super Bowl titles might have helped Emmitt Smith's status. He's the all-time rushing leader (18,355 yards) and played on three Super Bowl championship teams with Dallas. Along with quarterback Troy Aikman and receiver Michael Irvin, Smith formed "The Triplets" and, no doubt, also was aided by an exceptional offensive line and strong defense.
"I think production counts for a lot, and Emmitt always produced," Shula said. "He may not have been as flashy as some other guys, but he gave you results. He was a big part of the reason that team was so good."
Conversely, Sanders, Sayers, Simpson and Eric Dickerson made the list without playing for teams that won championships, and Payton's Chicago Bears didn't reach the Super Bowl until nearly the end of his career.
"I don't want to take anything away from Emmitt at all," said Robert Smith, who ranked Emmitt Smith at No. 6. "But I would have liked to have seen Barry Sanders running with that team. When you factor in size and the team he was playing with, Barry was probably working with the least of anybody and he still got the most out of it."
At 5-foot-8 and 203 pounds, Sanders was blessed with exceptional speed and cutting ability but was cursed because he landed with the Detroit Lions, who lost during much of his career. But Sanders did help the Lions win a playoff game in the 1991 season (the franchise's only postseason victory since 1957).
Before the 1999 season, Sanders, who was closing in on Payton's all-time rushing record, stunned the football world by retiring. He later admitted his decision stemmed from frustration over Detroit's lack of success and concerns about the franchise's future.
"I just wish that Barry Sanders hadn't retired when he did," said Thomas, who will be inducted into the Pro Football Hall of Fame in August. "He still was at the top of his game and could have gone on a long time."
Sanders wasn't the only runner on the list whose career ended prematurely. Sayers entered the league in 1965, but two major knee injuries ended his career by 1971. No player on the list drew more varied opinions than Sayers. Levy split his No. 1 vote between Sayers and Payton while two other panelists left Sayers off their lists, saying his career wasn't long enough.
"If Sayers didn't have the injuries, he would have been the best player in history," Levy said. "He was the smoothest, most unbelievable athlete ever."
Bushofsky, who voted Sayers at No. 3, acknowledged that he's a fan of durability. "But I'll make an exception on this one," Bushofsky said. The guy averaged 5 yards a carry and almost 12 yards a catch. You can't leave him off."
Who's left out
Plenty of other great running backs were left off the list.
"I'm looking at the rest of my list and seeing guys like Curtis Martin, Thurman Thomas, Jim Taylor, Terrell Davis, Tiki Barber, Fred Taylor and Marcus Allen," Reeves said. "It's very hard to leave names like that off."
All those names got strong consideration. So did Earl Campbell, Franco Harris, Tony Dorsett, Larry Csonka, John Riggins and Shaun Alexander. On the flip side, Simpson did make the list, despite his postcareer legal issues.
Simpson, who became the first to break the 2,000-yard barrier in 1973, appeared on six of the eight ballots and was rated as high as No. 2.
"People may want to forget it now," Reese said. "But for a time, O.J. was the face of the NFL."
The faces have changed with time. From Brown's power to Payton's grace to Sanders' speed, the qualities of the best running backs are constantly evolving. These days, Tomlinson is the standard for running backs.
Tomlinson, Alexander, Fred Taylor and Adrian Peterson were the only active running backs to receive votes from the panel. Alexander and Taylor came close to making the list. Peterson, who will enter just his second season after an outstanding rookie campaign with Minnesota, will have to put in much more time.
Tomlinson already has been in the league for seven years and has 10,650 rushing yards and 3,375 receiving yards and 129 touchdowns.
"If Tomlinson keeps going the way he is, call me back in a few years," Shula said. "We might have to put him at the top of the list. If Peterson keeps playing like he did as a rookie, call me back in 10 years and we might have to redo the whole list."
Pat Yasinskas covers the NFL for ESPN.com.