Samaje Perine has averaged 3.2 yards per carry over the first nine games of his rookie season. (John McDonnell/The Washington Post

It’s time for the Redskins to put their season on Kirk Cousins’ shoulders. Coach Jay Gruden should consider permanently dropping him back in the shotgun formation. Running the ball has gotten the Redskins nowhere.

Measly 2-yard runs and failed attempts on third-and-short have become the norm. Washington may not have a back run for 500 yards this season. That hasn’t happened since Clinton Portis led the team with 494 yards in 2009. Washington hasn’t had a 1,000-yard rusher since Alfred Morris ran for 1,074 yards in 2014.

Starting running back Rob Kelley was placed on injured reserve Tuesday with an MCL sprain and an ankle injury. Washington also signed Byron Marshall off the Eagles’ practice squad, but he’ll fit in behind rookie Samaje Perine and Chris Thompson. Perine is a short-yardage back who’s averaging 3.2 yards per carry. Thompson’s 4.6-yard average seems lofty, but the Redskins can’t risk playing him every down.

The Redskins may need to use next year’s first-round pick on a running back, even if this draft class seems devoid of a candidate who will make sense to take with a mid-round choice, where the team will likely be selecting.

The Redskins are paying Cousins like a franchise quarterback, so they should spend the final seven games deciding whether he’s worth the $28 million or more it will take to sign him for next season.

At 4-5, Washington is a long shot to make the playoffs anyway. The Redskins might as well develop young receivers Josh Doctson, Ryan Grant and Maurice Harris by increasing their targets.

Despite Gruden’s insistence that Perine will improve with more playing time, there’s little evidence he’ll learn to gain yards after contact.

Guard Brandon Scherff and tackle Morgan Moses both pull well and block defenders at the second level, but Redskins runners have struggled to take advantage.

Now that the entire starting offensive line is healthy enough to play together again, Cousins should have more time to throw. That is, if he can ignore the “trash” at his feet — pass rushers reaching for his legs ­— that he referenced in a very Robert Griffin III-like shot at the line after losing to Minnesota on Sunday.

Gruden has committed to the run more this season than his first three years. Washington has only 81 more pass attempts than running plays this season — just nine more per game. Gruden will insist the passing game can only succeed if the threat of running keeps linebackers close, but opponents no longer fear Washington’s runners. They’re defending short passes instead.

Gruden needs to play to his offense’s strength. Continue to use Thompson as more of a receiver and go with four wideouts. Running the ball is worthless until he has a worthy running back.

Read more columns from Rick Snider:

The Redskins’ defense has historically employed mercenaries. This year it has leaders.

While Redskins fill up the training room, their season is heading to the morgue

Kirk Cousins will have to carry the Redskins’ offense behind an injured line

The Redskins’ passing attack doesn’t have a No. 1 receiver, and it’s working anyway