(Wade Payne/Associated Press)

One preseason game down, three more to go before the Washington Redskins reach the regular season.

Thursday night the team, as Coach Mike Shanahan said, did some things well and some things poorly. But now the benchmark has been set and the team can focus on improving.

Here are five observations from the 22-21 win over the Titans:

1.) Lessons for Rambo: You knew the Georgia product would take his lumps here and there, and Bacarri Rambo was embarrassed on his first tackle attempt of the game as Chris Johnson juked him so badly that Redskins trainer Larry Hess might’ve considered checking the rookie safety for broken ankles after Johnson raced 58 yards to the end zone. Few players have the speed to match Johnson, and Rambo wasn’t the only player to whiff on a tackle attempt on that play. But the rookie saw first-hand just how great the difference between the speed of the college and NFL game. Said Rambo said: “That’s something I wasn’t expecting. But only thing I can do is learn from it, just get in the film room, talk to the coaches and the vets and try to learn things: how to take better angles and stuff like that.” Rambo found himself chasing Shonn Greene to the end zone on a 19-yard run as well.

As former NFL safety Matt Bowen said when I talked to him earlier this offseason about what lies ahead for the rookie defensive backs, it’s not really a bad thing for them to get toasted here and there early on, “because that’s how you learn.” Rambo, a film junkie, will go back and watch film over and over to figure out how to correct his shortcomings. One other positive: Rambo didn’t give up any big pass plays. Actually, Jake Locker didn’t even go after Rambo. The rookie took that as indication that he did his job in pass coverage.

2.) Cousins’s growth: As Shanahan often says, practices are crucial, but you really learn about a player once he gets out under the lights, and Cousins looked much better against Tennessee than he has in training camp practices. His passes had pinpoint accuracy, and his one incompletion was originally ruled a catch and fumble out of bounds before being reversed. The ability to read the defense and take what was given to him rather than try to force things showed great maturity and poise. Next week Cousins’s snap count should increase. He’ll try to show he can remain just as effective under a heavier workload.

3.) Quality depth at RB: We have yet to see rookies Jawan Jamison or Chris Thompson, but it’s evident that the depth at running back has improved this season. Roy Helu Jr. and Evan Royster have different styles, but each averaged 4.4 yards per carry in their first game audition for the No. 2 back duties. Meanwhile, Keiland Williams sought to remain relevant as well, averaging 5.5 yards per carry on two touches. Helu and Royster looked more confident in pass protection than they have in the past, which is extremely important. Neither had a pass come their way, but that versatility will help. Helu showed good patience in letting running lanes open up, which is something he has had to be mindful as he returns from roughly a year-long layoff. He said he ran more with his eyes, which is something Royster does a good job of as well. If Thompson can contribute as the versatile, speed threat coach believe he can provide, Shanahan and Co. could have some tough decision to make.

4.)  Tackling problems: Rambo wasn’t the only defensive player who struggled in the tackling department. His veteran teammates, including London Fletcher, Brian Orakpo, Stephen Bowen and Jarvis Jenkins all came up short in the run-stopping department. Orakpo said the team has to make significant improvements here. The linebacker wasn’t overly concerned, however, because Thursday marked the first time that the defense has really tackled. (In practice, they do a lot of tagging and light wrap-ups to avoid causing injuries).

Orakpo said discipline is key. He said he and his teammates must maintain their gap assignments, and not get so wrapped up mentally with the idea of getting into the backfield and to the quarterback that they over-run ball carriers. The team was without Barry Cofield – very key in the run-stopping attack – so his presence could help in this department.

5.) Griffin dressing: Yes, he wound up being part of the story despite not even playing. I can’t say I’ve ever seen a player who has been ruled out of the game dress anyway and appear as if he could take the field at any moment, but there was Robert Griffin III in full uniform, helmet, knee brace and all.

Shanahan said that he offered Griffin the opportunity to go through pregame warmups so the quarterback could get some more work since he isn’t playing this preseason. Griffin added during a brief locker room chat that he planned to dress even though he wasn’t playing because he doesn’t see himself as injured and wanted to go through the usual pregame rituals as just another step toward his return.

It’s evident that Griffin’s confidence is high. He wants badly to be back on the field and wants to get as close to that as possible so when he does get that green light, the mental transition is as seamless as possible. Next game Shanahan may have to assign security to ensure Griffin doesn’t try to slip into the game. Okay, that’s a joke. Maybe.

Post photos from Thursday’s preseason opener:

Have a Redskins question? E-mail Mike Jones at mike.jones@washpost.com with the subject line “Mailbag question” for him to answer it in The Mailbag.

Follow: @MikeJonesWaPo | @MarkMaske | @D3Keith @Insider | @PostSports

More on the Redskins:

Ups and downs in the Redskins’ preseason triumph in Tennessee

Reid: A lot to learn yet for young defensive backs

Orakpo and Davis are bright spots in preseason opener

Davis regrets penalty for excessive celebration

D.C. Sports Bog: Davis tasers himself, earns a penalty | More Bog

Photos from Nashville | Thursday night’s statistics