MINNEAPOLIS -- Now that we're a quarter of the way through the 2015 NFL season, and Adrian Peterson's comeback has him in a familiar place atop the NFL rushing leaderboard, it seems like a good time to take a closer look at Peterson's season so far. Here are five things to know:

1. He's on pace for a top-10 year for a 30-year-old running back, and would be the first 30-something rushing champ in 11 years: Peterson is currently on pace for 1,488 yards, which would be the eighth-most in NFL history by a running back in his 30s, and the fifth-most for a back at age 30. If Peterson stayed on this pace, he'd finish right behind Barry Sanders, who ran for 1,491 yards at age 30 in 1998 (what turned out to be his final season). Interestingly enough, only eight backs in NFL history have run for 1,000 yards in their 30s while matching or exceeding Peterson's current 4.96-yards-per-carry average. If Peterson wins the rushing title, he'd be the first back to do it in his 30s since Curtis Martin in 2004.

2. He's getting most of his carries the old-fashioned way -- and it's working: Fifty-five of Peterson's 75 carries have been with Teddy Bridgewater under center, and there's a good reason for it: He's still getting most of his yards that way. According to ESPN Stats & Information, he's averaging 5.95 yards per carry that way, compared to 2.25 yards on his 20 shotgun and pistol carries. The Vikings want to have Peterson involved in their passing game, they can run packaged plays off zone read looks in the shotgun and they need to avoid tipping their hand about a run vs. pass when Bridgewater is under center; he's only thrown 24 of his 115 passes when starting under center, according to ESPN Stats & Information. But when Peterson is still the Vikings' most effective weapon, it makes sense to structure the offense around what he does well, at least for now.

Adrian Peterson already has four runs of 20 yards or more this season. AP Photo/Marcio Jose Sanchez

3. He's still breaking big runs: Peterson's 48-yard TD run on Sunday against the Broncos was his longest of the season, and might have been the clearest example of his breakaway speed coming back. Peterson didn't play in the preseason, went 53 weeks between games and admitted he didn't feel quite right about his conditioning before the Vikings' Week 3 win against the Chargers. His long speed might not be quite at his peak, but he still has plenty to outrun defenders much of the time. Peterson has four runs of 20 yards or more already this season; if he follows that pace, he'll end the year with 16 runs of 20-plus yards, which would be the third-most of his career. "Once he hit that crease (on Sunday), I didn't see less speed than I saw before," general manager Rick Spielman said on Tuesday. "Just watching him practice, he's Adrian Peterson. He's a unique player."

4. He's still struggling in pass protection: Peterson took the blame for missing a blitz pickup of T.J. Ward on the Broncos' safety's decisive forced fumble of Teddy Bridgewater on Sunday, and was beating himself up for missing a block on the shovel pass Bridgewater threw him in Week 2; Peterson turned that play into a 49-yard gain. That's cost Peterson some playing time, and a chance to be more involved in the passing game, like the Vikings hoped he would be. According to ESPN Stats and Information, he's only been on the field for 21 of the Vikings' 48 third downs on offense, and for just 11 of the 34 plays where the Vikings have faced third-and-5 or longer. Considering the Vikings don't run an empty backfield, it's worth noting when Peterson isn't in the game. "He’s working very hard at it," coach Mike Zimmer said. "We kept him in there on some third downs this time, so we’ll keep going with it. The thing about Adrian is that he doesn’t just say, “Hey, I’m a running back, I don’t want to work on it.” He wants to work on this. He wants to be out there as much as he possibly can, so he’s committed to becoming a better pass protector and I believe he is."

5. He's on pace for a pay cut in 2016: The restructured deal the Vikings agreed to with Peterson before the season will pay him a $3 million roster bonus in 2016. Peterson can push it up to $5 million, but only if he runs for 1,900 yards and the Vikings win the Super Bowl. It would total $4 million if he runs for 1,750 yards and the Vikings reach the NFC title game, and would be $3 million if he runs for 1,550 yards and the Vikings win a playoff game. If Peterson fails to reach 1,550 yards and the Vikings don't win a playoff game, the bonus would be $2 million. And if he doesn't reach 1,350 yards and the Vikings miss the playoffs, the bonus is $1 million. So essentially, Peterson is on pace for a $2 million bonus, provided the Vikings win a playoff game. That'd be a $10 million cap figure for the Vikings to keep Peterson at age 31. or a $9 million figure if Peterson's production falls off or the Vikings don't get their first playoff win since 2009.