Adrian Peterson is going to miss several months to undergo knee surgery, and his future in the NFL is suddenly up in the air

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The Minnesota Vikings announced on Wednesday that running back Adrian Peterson will have surgery on his knee after spraining his MCL in Week 2 against the Green Bay Packers.

The surgery will be performed on Thursday and will likely keep Peterson out several months.

According to the NFL Network, there's hope Peterson could return in December for a playoff run, but ESPN noted head coach Mike Zimmer conceded there's a chance Peterson will be out for the season.

It's brutal news for the Vikings, who looked promising in a Week 2 win and are already dealing with the loss of quarterback Teddy Bridgwater for the season. In the meantime, it's raising questions about Peterson's future in the NFL.

Prior to the injury, Peterson was already putting up mediocre numbers through two games. He had just 50 yards on 31 rushing attempts, for an average of 1.6 yards per attempt, with no touchdowns. Dating back to last season, Peterson has topped 100 yards once in his last seven games.

In 2015, Peterson ran for 961 yards with an average 4.8 yards per carry through his first nine games, then just 524 yards with an average of 3.7 yards per carry in the final seven games. And over those final seven games, if we remove one 158-yard performance against the Falcons (who ranked 25th in run defense), that total is down to 366 yards over six games.

This is not to say Peterson is no longer effective, but clearly, after his ninth game last year, there's been something of a downturn in his performance. And that is to be expected. Peterson is 31 years old with 2,412 career carries and has already recovered from a torn ACL in 2011. There's a lot of mileage on his legs.

Furthermore, Peterson is scheduled to make $18 million next season, a giant number for a 32-year-old running back coming off his second serious knee injury. The Vikings could ask him to restructure his contract or they may just cut him, depending on how his recovery goes. Restructuring his contract would be a possibility, but it would likely require a huge bonus payment in some fashion to lower his cap number.

Peterson will still have value to teams, including the Vikings. However, it's very possibly the end of his time as a premier back in the NFL. He could carve out a nice role sharing the rock with teams around the NFL (imagine him in a mentor role to Ezekiel Elliott behind the supreme offensive line with his hometown Cowboys!), including on the Vikings.

In an age when teams focus less and less on running backs, Peterson's past can only take him so far. Given his age, injury history, and big contract, it's unlikely Peterson will return to the same role, whether it's this year or next.

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