The way Kirk Cousins remembers it, the transformation in his thinking about his situation with the Washington Redskins began a month or so into his tenure with the team, well ahead of when there was a tangible reason to support such a change.

It was May 2012, not long after Cousins had been drafted only three rounds after the team chose its centerpiece-to-be, fellow quarterback Robert Griffin III. This was long before Cousins orchestrated two key victories down the stretch for the Redskins last season as the stand-in for an injured Griffin. This was before Cousins spent this past offseason and the early stages of this current training camp practicing with the starting offense while Griffin works his way back from knee surgery in January. So there was no evidence at the time that Cousins held the promise of becoming a starting quarterback in the NFL.

Cousins and some of his Redskins teammates, he recalls, had piled into a rental car and driven to downtown Washington. They spent time walking around the city. That’s when it began to strike Cousins, he says, that maybe, just maybe, it wasn’t quite so hopeless, quite so unquestionably career-stifling, to break into his profession as the understudy to a football phenomenon.

“I remember thinking, ‘This is a pretty cool place to be, a pretty cool city to play for,’ ” Cousins said. “I started to really make it home at that point. And I think through training camp and into the preseason last year on the football field was when it really started to click. And I felt like while everything may not happen right away, if I can be patient, this could be the best thing that ever happened to me.”

Embracing his role

When the Redskins open the preseason Thursday night in Nashville against the Tennessee Titans, it will be Cousins, not Griffin, in the lineup at quarterback. Griffin has been on the training-camp practice field, but Coach Mike Shanahan’s plan is to withhold his mending star from the Redskins’ entire preseason schedule.

Washington Redskins quarterback Kirk Cousins discusses his book “Game Changer: Faith, Football and Finding Your Way” and how he handles being the back-up to one of the most popular athletes in the world. (Jayne Orenstein/Post Sports Live)

The initial mini-uproar over Shanahan using a fourth-round pick on Cousins, rather than addressing other needs, in the same draft in which the Redskins selected Griffin second overall has long since subsided. Cousins helped beat the Baltimore Ravens last season while subbing in the late stages for an injured Griffin. With Griffin sidelined, he engineered a triumph in Cleveland in his first NFL start.

“In the Baltimore game and in the Cleveland game, he showed us that there’s no drop-off,” veteran Redskins cornerback Josh Wilson said. “RGIII is an amazing talent. But God forbid if something was to happen to him, there’s not going to be a drop-off. You’re going to have someone that can lead this team to victory.”

And the value of being with the Redskins has become increasingly evident to Cousins, building ever since that initial realization while he walked around the city.

“Now I understand the great opportunity I have to learn from the Shanahans,” Cousins said. “I understand the great franchise I’ve been able to play for. I understand the history now and the winning tradition and I love living in D.C. I knew nothing about D.C. before moving out there. There are so many positives I knew nothing about when I was first picked.

“Obviously the one glaring situation is I am a backup. And I would love to be a starter someday. But I’ve got my hands full learning this offense, trying to become a better quarterback still as a backup. I think it’s not the worst thing in the world to be able to develop more in the anonymous, behind-the-scenes role for right now.”

Cousins knows his role and is careful never to overstep his bounds, always acknowledging that this team is Griffin’s once last season’s NFL offensive rookie of the year returns to full-time duties. Most seem to expect that to happen in time for the Sept. 9 regular season opener. Cousins’s chance to be a starter, if indeed it comes, is virtually certain to come elsewhere. The questions are where and when.

Trading him at some point could enable the Redskins to recoup a draft choice or two, particularly important for a team that sent a trio of first-rounders and a second-rounder to the St. Louis Rams in order to land the pick used on Griffin. But Cousins said he never expected, even before Griffin got hurt, to be traded this past offseason and, in fact, he thinks it’s possible he’ll stay put for the duration of the four-year contract he signed after being drafted.

Jonathan Forsythe talks to “RG3: The Promise” author and Post sports writer Dave Sheinin about what is next for Robert Griffin III and the Redskins. (Post Sports Live)

“My mind-set was always I would probably be here for a good while, maybe even for the length of my first contract,” Cousins said. “I think that I have something I can offer this team, even if it’s just as a backup and in a limited role. I was never thinking it would be that fast. . . . I’m only as good as my last performance. The tough thing in my role is I do have a limited role. So if I go out there and lay an egg, it negates everything you’ve done in the past. You have to really take advantage of those limited opportunities.”

‘Patience is difficult’

His career-path role model, Cousins says, is Matt Schaub, the two-time Pro Bowler for the Houston Texans who began his NFL career as Michael Vick’s backup for three seasons in Atlanta. But Cousins acknowledges that “patience is difficult, no matter who you are.” Waiting is not in vogue these days for NFL quarterbacks, not after Griffin, Indianapolis’s Andrew Luck and Seattle’s Russell Wilson crafted the year of the rookie quarterback last season. Two other rookies, Cleveland’s Brandon Weeden and Miami’s Ryan Tannehill, also were season-long starters.

Is Cousins ready now to be an NFL starter? He concedes there is no way to know with certainty.

“It’s hard to answer until I would get the shot. . . . I’m certainly more ready now than I was a year ago,” he said. “Could I have done the job last year? Maybe. Hopefully. Probably. Could I do a better job this year? Certainly. From this year [to next year], from Year 2 to Year 3, I could probably do an even better job.”

The Redskins say they see growth in Cousins’s game, particularly after working with the starters in offseason practices.

“I see him going through his progressions a lot faster,” wide receiver Josh Morgan said. “I see him taking more control over the offense. He’s getting more comfortable just being the leader, being more of a leader because he knows his role. He knows the whole offense. He’s like a computer. He knows everything. He breaks everything down at every position. He could tell you everything about the whole offense. . . . The way he says it, it’s like he’s programmed because he says it just like [offensive coordinator] Kyle Shanahan puts it in. So it’s kind of weird. . . . You see more of his personality the more comfortable he gets, too. You see more of the Captain Kirk come out.”

Cousins will have to step aside when Griffin makes his full return. It might seem that would be more difficult for Cousins after the taste that he’s had of being the starter during the offseason and training camp. But Cousins says that’s not the case.

“What it actually does,” he said, “is it makes me more confident, makes me believe that if I do get called into duty on maybe limited reps on a week of practice in a normal season week, I’ll be ready to go. I think last year there was some doubt that, ‘I haven’t really practiced and this is tough as a rookie and I’ve got to be ready to go on limited reps.’ And now I’ll have more confidence and a greater belief that even when I’m not getting reps, I know that I’ve gotten so much experience in the past. That can really help if I do have to go in.”