Bud Grant led the Vikings to four Super Bowls during his 18 seasons as coach and has seen a lot of great running backs.
And Grant said he believes that Adrian Peterson, who rushed for 212 yards in the Vikings' 36-22 victory at St. Louis on Sunday, is the type of running back that the NFL hasn't seen for some time.
However to go down as an all-time great, Grant believes Peterson has to continue what he has done over his first six NFL seasons for a few more years. He has to prove he can compile statistics similar to Walter Payton, the Bears great who amassed 16,726 rushing yards from 1975 to '87.
Asked to compare Peterson with Chuck Foreman, the star Vikings running back of the 1970s, Grant said they are different types of runners.
"[Peterson] is faster than Foreman. But Foreman was a bigger back," Grant said, before pointing out that Foreman only played eight NFL seasons. "... If Foreman had played 10 or 12 years, he might have been one of the greatest of all time."
Grant, a great judge of talent, believes it is hard to evaluate running backs until they are done. The NFL's career leading rusher, Emmitt Smith, played 15 seasons.
Grant said Peterson does have a combination of talents that some great backs of the past didn't have.
"If Adrian can continue to play at this level for a couple, three more years, he can go down as one of the greatest," Grant said. "Peterson has a combination of strength and speed. Not all running backs have that. Some are fast, some are strong, some are evasive, but Adrian has a combination of strength and speed. He can break through tackles, and he can also outrun people."