With their three-day rookie minicamp in the books, Washington Redskins Coach Mike Shanahan said Sunday he was encouraged by the early impressions made by defensive backs David Amerson, Phillip Thomas and Bacarri Rambo.

Drafted in the second, fourth and sixth rounds, respectively, to help upgrade a secondary that struggled last season, Amerson, Thomas and Rambo — as well as their four fellow draft selections, 12 undrafted free agent additions and 48 tryout players — received a crash course in Washington’s playbook. Friday and Saturday featured classroom sessions and two practices each day at Redskins Park. The camp wrapped up with more meetings and one practice Sunday.

The rookies still have plenty to learn. But the camp gave them a foundation to build on, and it afforded Shanahan and his coaches an up-close look at the prospects selected in the NFL draft at the end of April.

“It was real impressive to see our draft choices and see their size and speed and their quickness, the things we were hoping for,” Shanahan said. “Their ball skills were very evident out there the last few days. It was a good practice.”

The size, speed and athleticism that made Amerson, Thomas and Rambo attractive to the Redskins certainly was evident. And they took well to the defense.

Amerson, a cornerback whom Shanahan has said the team will groom to play on the outside, worked almost exclusively on the right side. He used his speed, height (6 feet 1) and long arms to create some problems for the receivers he went against.

Amerson played in a different system at North Carolina State, so he spent the weekend familiarizing himself with Washington’s scheme. He said he’s excited about the playmaking opportunities that the Redskins’ system will afford him.

“I think the defense is very corner-friendly,” Amerson said. “At N.C. State, our corners were often out on an island. But here, you’ve got a lot of help over the top, so you can be aggressive when it comes to jumping routes and things like that, and that’s how I love to play.”

Thomas and Rambo shared the field, with Thomas lining up predominantly at strong safety and Rambo at free safety. There were times when the offensive formation and its motions required Rambo to play closer to the line of scrimmage while Thomas dropped back and played deep. Other times, they both played deep.

Both displayed good anticipation and appeared fluid while backpedaling and changing directions, then converging toward the ball.

Thomas recorded an interception and also forced a fumble while covering wide receiver Skye Dawson, who made a catch as he ran a slant pattern. Thomas swatted and knocked the ball out of Dawson’s grasp, then scooped it up.

Rambo also had an interception downfield as he went in traffic and wrestled a Ryan Radcliff pass from wide receiver Jason Thompson.

“It’s kind of better than I thought it was going to go,” Rambo said. “Came out here and just learned what to do. Kind of carried over from what we did [in college] at Georgia. Coach Kirk Olivadotti, who’s a linebackers coach there, used to be here, so I had a year to learn things from him, and they carried over, and I’m just taking advantage of everything and learning the scheme. Learning the scheme, learning technique and coverage, and it was all natural after that.”

For Thomas, the concepts of Washington’s defense were familiar. His college team, Fresno State, ran virtually the same system. So the only thing that was foreign for Thompson was the terminology. But he said he understood his role well.

“I felt comfortable playing wherever they play me: strong, free, wherever,” he said. “We repped it a little bit this week, and I got comfortable as the week went along.”

Shanahan said the intelligence, athleticism and versatility seen in the safeties confirmed the pre-draft assessments Washington conducted on each.

“Well, when we drafted them — we have different tests that they take that tell us what type of mental quickness they have and what type of dedication, commitment — those types of things that are very important to us,” Shanahan said. “Those two guys — one had a 10, one had a nine out of a 10-point [scale], so that’s as good as you see, and that’s what you’re hoping for.”

He also said: “The good part about them is they’ve got the size and athletic ability. I think everybody knows what kind of receiving skills they have. . . . I think both of them could do a great job at the strong safety for us as well as the free safety position.”

Notes: Tight end Jordan Reed, a third-round draft pick, did not partake in the minicamp practices because he still is healing from an injury to his left knee and quadriceps. . . . Running back Chris Thompson (fifth round), who is recovering from surgery to repair a torn anterior cruciate ligament, also watched. Shanahan said Thompson remains on target to be a full participant by the start of training camp. . . .

Starting running back Alfred Morris’s little brother Shawn Morris was a minicamp tryout participant. Shawn, a Division III all-American from Birmingham Southern, is a running back. . . . Former Western Illinois guard Andrew Robiskie, the son of former Redskins offensive coordinator and interim head coach Terry Robiskie, was also a tryout participant. Shanahan and Terry Robiskie coached together with the Los Angeles Raiders.