Future Hall of Fame running back Adrian Peterson signed with the Redskins on Monday. The reason he had to wait until Aug. 20 to latch onto a new team is because Peterson has been incredibly ineffective over the past two seasons, averaging 3.1 yards per carry. The reason he's averaged 3.1 yards per carry over the past two seasons is probably because Peterson is older than 30 and like every running back before him, age has seemingly sapped the electrifying talent out of him. And the only reason the Redskins signed him is because they lost Derrius Guice to a season-ending injury during the preseason.

That's the most logical way to assess how Peterson got to this point in his career. But it should come as no surprise to hear that Peterson and the Redskins are fighting back against the notion that Peterson is too old to be an effective runner.

 On Tuesday, Peterson took aim at those who say he's too old.

"They don't know football," Peterson said, according to NFL.com.

Meanwhile, Redskins coach Jay Gruden explained that the Redskins signed Peterson because of Peterson's physical conditioning.

There's no denying that Peterson was one of the game's greatest running backs. In his career, most of which he's spent with the Vikings, some of which he spent with the Saints and Cardinals, Peterson has rushed for 12,276 yards (12th all time) and 99 touchdowns (tied for ninth with Barry Sanders). He's fourth all-time in rushing yards per game (92.3) and he's owns the second-best rushing season ever (2,097 yards in 2012). At his peak, he was a marvel. And he's going to finish his career in Canton.

But Peterson isn't what he used to be. Last season, playing for both the Saints and the Cardinals, he totaled 529 yards and two touchdowns in 10 games. At times, there were flashes of his former self (134 yards against the Buccaneers and 159 yards against the 49ers), but most of the time he looked like a 32-year-old running back with ~2,500 career carries weighing him down.

Maybe Peterson will find a way to rejuvenate his career in Washington. But all signs indicate that Peterson's days as a RB1 are over, regardless of what Peterson and his new team are saying. Remember, a year ago, the Saints were raving about Peterson. They ended up trading him by mid-October. At this point, we'll need to see Peterson play at a high level before we fully believe in his return.

The good news: Gruden wants to play him as early as this Friday. So, we might not have to wait long to find out how much Peterson has left in the tank.