Through the first six weeks of the season, the NFL rushing leader is a rookie who has just the 14th-most carries in the league. He has only one game with more than 20 runs, and isn't even regarded by his head coach as the starter for a franchise with a losing record.
Well, at least not nominally.
Listed second behind the veteran Chester Taylor on the Minnesota Vikings' tailback depth chart, first-round draft choice Adrian Peterson is first in the NFL in rushing yards (607) and yards per carry (6.3).
And, risking redundancy here, he's not the starter, according to Vikings head coach Brad Childress.
Which doesn't make the former University of Oklahoma star less special. Actually, it puts Peterson in pretty good company, considering this is a season in which reserve tailbacks have played prominent roles across the league.
"A lot of backups have put up [big] numbers when given the chance," said Derrick Ward, who leads the New York Giants in rushing with 424 yards after having been pushed into the lineup after starter Brandon Jacobs suffered a knee injury. "Every team wants to have the so-called 'feature back,' sure. But I don't think you can get by with just one guy anymore. You have to have a second [runner] who produces for you."
No backup runner, of course, has produced quite like Peterson. His upright running style, thoroughbred-like gait and rare combination of raw power and breathtaking speed have drawn justifiable comparisons to Hall of Fame tailback Eric Dickerson. Still, it has been a month-and-a-half stretch of the season during which a number of No. 2 tailbacks already have made their marks while making plenty of yards.
There have been 14 games of 100 or more rushing yards by tailbacks who either began the 2007 season as backups, or started individual games on the bench. Only in Week 2 did the schedule fail to produce a 100-yard outing from a reserve tailback. There have been three weeks in which at least four backups ran for 100 yards.
Three of the top 10 rushers in the league entering this weekend are players who began the season as backups. There are nine former backups among the top 25 rushers and 12 in the top 35 runners in the league. The leading rushers on six of the 32 teams are backs who began the season as reserves.
Included in that group are excellent runners such as Marion Barber III of Dallas, New England's Sammy Morris and Maurice Jones-Drew of Jacksonville. Those are tailbacks of all shapes and sizes, but with one common denominator: None of them really thinks of himself merely as a stand-in for the No. 1 back.
"You've got to believe in yourself," said Morris, who posted a pair of 100-yard outings while replacing an injured Laurence Maroney in the lineup, but who now could miss about a month himself because of a chest injury. "And whether you're getting a start because the other guy is hurt, or just getting eight or 10 carries giving the starter [a break], you have to make every carry count. Because it's always going to be about production in this league, no matter who you are."
In fact, some of the 100-yard performances by backup tailbacks in 2007 have come from backs who, frankly, aren't very well known by people outside their own immediate families or locker rooms. Kenton Keith, a CFL refugee signed by Indianapolis as a free agent in the offseason, ran for 121 yards and two touchdowns on 28 carries, substituting for an injured Joseph Addai in Week 5.
A week earlier, Oakland's Justin Fargas, a speedster long on potential but shy of credentials because he's been injured for much of his five-year career, rang up 179 yards on 22 carries, replacing LaMont Jordan.
There have also been standout rushing performances from better-known backups such as Jones-Drew, DeAngelo Williams of Carolina, Philadelphia's Correll Buckhalter, Barber, Morris and Michael Turner of San Diego.
Turner, who ran for 147 yards on just 10 attempts against Denver on Oct. 7, while spelling LaDainian Tomlinson in a lopsided game, figures to ditch the backup label in the upcoming offseason. He almost certainly will be one of the league's most coveted unrestricted free agents. But for now, like most No. 2 tailbacks, he understands his role.
"When they give it to you," Turner said, "you better do something with it."
So far in 2007, backup tailbacks certainly have.
Len Pasquarelli is a senior writer for ESPN.com.