Pro Football Focus has become an integral part of the NFL since they were created in 2006. Eventually, Cris Collinsworth purchased it in 2014, and they took off from there. As they enter their 20th season covering and grading the NFL, they are taking a look at the best players in their history they have covered and graded. Their writer Nathan Jahnke explains, "As part of PFF's celebration of 20 years of NFL data, we've built an All-Star team for every franchise, highlighting the best players at each position from the PFF era. This final installment looks at the entire league, making an All-PFF first and second team."On the list was several former Vikings with the biggest being Adrian Peterson. He was listed as the RB2 behind Derrick Henry. They explained his placement, writing, "Henry and Peterson both had more good seasons to pick from. If this team had a specific third-down or receiving back, McCaffrey would have been the clear choice. In the battle between Henry and Peterson, Peterson received more help from his offensive line at 1.6 yards before contact per carry. Notably, Henry had more yards after contact per carry at 3.6 to 3.0, a higher avoided tackle rate, a higher first down rate and much fewer fumbles."Joining Peterson in controversial fashion is Harrison Smith, who was a first-team safety alongside Eric Weddle. They earned the spots over Hall of Famers Ed Reed and Troy Polamalu. They explained the rankings, writing, "Eric Weddle,Harrison SmithandDevin McCourtyare three of the five safeties with over 12,000 snaps during the PFF era and three of the five with grades above 90.0. All three own grades above 92.0 in both run defense and coverage. Pass-rushing helped differentiate the three, as Weddle and Smith blitzed much more than McCourty and were more successful on a per-play basis."This article originally appeared on Vikings Wire: Several Vikings named on PFF's list of best players since 2006