Running back Samaje Perine (32) had six carries for 15 yards Thursday. (John McDonnell/The Washington Post)

RICHMOND — Redskins Coach Jay Gruden didn’t attempt to put a positive spin on the performance of his starting offense in Thursday’ preseason loss at Baltimore. The unit was on the field for just six plays, failed to get a first down and lost one yard before retiring for the night.

Nor did he sugarcoat the debut of rookie running back Samaje Perine, who fumbled once, dropped a pass and didn’t hit open holes as violently as coaches wanted to see. That said, Gruden made clear he’s not losing faith in the rookie, who rushing for more than 1,000 yards in three consecutive seasons at Oklahoma.

On defense, it took just one preseason game to thin out the enviable depth that the Redskins enjoyed at outside linebacker at the start of training camp.

Along with the season-ending knee injury to fourth-year player Trent Murphy in the deflating 23-3 loss, rookie linebacker Ryan Anderson, who was a bright spot in the game, suffered a stinger and isn’t expected to practice much Friday, Gruden said before the team regrouped for practice in Richmond. Murphy was placed on injured reserve.

Outside linebacker Junior Galette, who was held out of Friday’s game with a sore hamstring, will likely miss the next six or seven days of practice, which could jeopardize his availability for the Redskins’ second preseason game.

But amid the bad news, there was some good, with Gruden reporting that tests showed that second-year player Su’a Cravens suffered no structural damage to his knee and will be reevaluated once the swelling goes down.

Gruden also said that rookie cornerback Fabian Moreau (pectoral) would be a full participant in practice Saturday, as well as rookie safety Montae Nicholson (shoulder).

Like quarterback Kirk Cousins, Gruden characterized the team’s poor showing in the preseason loss as “a wake-up call” — particularly his starting offense.

“Six plays that weren’t as productive as I would have liked,” Gruden said, calling it “a good learning experience for our guys. … They’ll know what to expect next week.”

Redskins running backs carried 18 times, averaging just 2.2 yards per rush.

Tight end Jordan Reed, who has been sidelined for some time by a toe injury, will be experimenting with a special orthotic for the next few days, Gruden added, to see if that helps his return to the field.

More on the Redskins:

Redskins and Richmond: A marriage in need of counseling?

Five observations from the preseason opener against the Ravens

Preseason is meaningless? Backup QBs would beg to differ.

Steinberg: The Redskins were pretty brutal to watch Thursday