The NFL's career rushing record isn't a number that's easily retrieved from the memory banks of fans, reporters or even the men who have played and coached the running back position at the highest level.

"It's 16,000 and something yards, right?" asked Vikings running backs coach James Saxon, who played for the Chiefs, Dolphins and Eagles.

Not quite. Try 18,355. That's what Emmitt Smith posted over 15 seasons for the Cowboys and Cardinals before retiring after the 2004 season.

Fifty-nine spots down the list at No. 60 is Adrian Peterson, the Vikings' four-time All-Pro and 27-year-old face of the franchise. With 6,752 yards in five seasons, he and his reconstructed left knee stand just 67 yards from passing Robert Smith as the Vikings' career rushing leader.

Peterson won't play this preseason. So it will be at least 18 days before collective breaths are held as he restarts his pursuit of Robert and Emmitt, although the latter Smith is still 11,603 yards away.

"That's a long, long way," Saxon said. "That's like here-to-Mars long."

Yes, but Peterson isn't the only active player who seems to be standing 33.9 million miles behind Emmitt. Especially when one considers how much the running back position has changed as the NFL continues its rapid evolution into a passing league.

With LaDainian Tomlinson, Thomas Jones and Ricky Williams now out of the league, the leading active rusher is Rams running back Steven Jackson, who ranks 32nd on the career list. He's already 29, but his 9,093 yards are less than halfway to Smith's mark. Meanwhile, the active leader among players 25 or younger is Baltimore's Ray Rice, 25, who ranks 153rd with 4,377 yards in four seasons.

Remarkably good health and luck over the course of more than 10 seasons is a must to challenge the record. In Smith's 13 seasons with the Cowboys, he missed just four games because of injury despite averaging 311 carries a year. As freakishly tough as he is, Peterson missed that many games last season alone.

Peterson has said before that he wants to be remembered as the greatest running back who ever played the game. He grew up rooting for Smith in Palestine, Texas, but considers Walter Payton the greatest running back ever.

"Where do we put Adrian on that list?" Saxon said. "I don't know. The book is still being written."

Even with good long-term health, the chances of anyone catching Smith are affected by the changing nature of the running back position.

"I never say never because every now and then there is one that comes around that is extremely durable and hits it right by staying healthy and being on a good team," Vikings defensive coordinator Alan Williams said. "But you're seeing so many more teams going with a two-platoon running back system. Guys are splitting all these reps because it's such a long season and the punishment is immense."

A year ago, 19 teams had at least two players surpass 100 carries. The Panthers had three, including quarterback Cam Newton. The Packers had two players combine for 267 carries. The split was 134-133. Meanwhile, the Saints drafted running back Mark Ingram in the first round and still chose to spread 79 or more carries among four players.

Now compare that to Smith's career. Only once in 13 years with the Cowboys did anyone other than Smith get 100 carries. In 1991, Smith had 365 carries, while the next-highest total was 17.

Meanwhile, as more teams split up carries, the evolution of the passing game also has hit overdrive. Last year, Drew Brees and Tom Brady broke Dan Marino's 25-year-old passing mark of 5,084 yards. Three passed for 5,000 yards, and 10 more reached 4,000. And, oh yeah, the Super Bowl champion Giants ranked dead last in rushing.

"I do think the game has changed," Vikings linebacker Chad Greenway said. "Teams are having more and more success and winning without having to rush the football. So, obviously, running the ball is becoming a little less important."

Where Peterson's career goes from here is something that only several more game days will reveal. But in his mind, Peterson believes his chances of catching Emmitt Smith are as good today as they were before that gruesome knee injury nearly eight months ago.

"I'm 11,603 behind Emmitt?" Peterson said. "Yeah, I can do it. How long did Emmitt play? Fifteen years? We'll see. But that would be cool.

"I'd be cheating myself if I said I didn't want to get that record. Yeah, the NFL has opened up more into a passing league. But, then again, when you have a dominant back who can make it happen out of the backfield, those guys will still touch the ball. A lot."

Mark Craig • mcraig@startribune.com