“When you draft 1-1 [two years in a row, the first time ever in the draft], it had better be impactful,’’ said Nationals senior vice president and general manager Mike Rizzo yesterday at Nationals Park. “Years will tell whether we were right or wrong.’’

Strasburg, 21, was last year’s first pick and it hasn’t taken him very long to get to the major leagues. Harper dominated at the College of Southern Nevada with a .443 average with 31 homers and 98 RBIs in 66 games using a wooden bat.

Harper, like Strasburg, is represented by Scott Boras, who returned a record four-year, $15.1 million deal for Strasburg (signing it 77 seconds before the deadline), and will likely look to surpass that with Harper, who is a 6-foot-3-inch, 205-pound lefthanded hitter, playing mostly at catcher. Rizzo said Harper will start as an outfielder and foresees him as a “prototypical package for a middle-of-the-lineup strong-armed right fielder.’’

The Nationals have until Aug. 16 to sign Harper. If they don’t, he could return to college or transfer to a four-year program.

Rizzo said the decision to make him an outfielder “will accelerate his development as a hitter and extend his baseball career.’’ The GM, who once was a scout for the Red Sox and, working for the Arizona Diamondbacks, drafted Justin Upton when he was 17, said assistant GM Roy Clark and scouting director Kris Kline have been watching Harper since he was 15.

Kline said Harper was a “cross between Larry Walker and J.D. Drew.’’

The first time Clark saw Harper he said, “Oh my gosh, who is this kid?’’ And then he was told he was 15.

A devout Mormon, Harper has developed well beyond his years. Rizzo described him as a “baseball rat. We’ve scouted him for a long time, we’ve done a lot of work on his family background and his character. This kid gets after it like few amateur players have. He’s a good kid, a very spiritual kid.’’

Rizzo also indicated he felt Harper was the only “three-hole hitter’’ in the draft.

Harper left high school after his sophomore season, received his general equivalency degree and enrolled at the College of Southern Nevada.

Just as there was never any doubt the Nationals would select Strasburg, there was no doubt about taking Harper, who is considered, like Strasburg, a once-in-a-generation talent.

The Nationals are following the path taken by the Tampa Bay Rays, who kept accumulating top talent with high picks in the draft. Those lean years have paid off for the Rays and they appear to be paying off for the Nationals, who have finished last five times in six seasons, and they are currently last in the NL East. But a playoff-type atmosphere is expected at the ballpark tonight.

Orioles third base coach Gary Allenson, who was recently the Triple A manager at Norfolk, was asked to compare Strasburg with Roger Clemens, whom Allenson caught with the Red Sox.

“They both blew right through the minor leagues, but I think Strasburg might be the more accomplished pitcher at the same age,’’ he said. “Roger had the great fastball and curve, and later developed the split. This kid has four pitches he can get you out with.’’

Strasburg went 7-2 with a 1.30 ERA in 11 starts between Double A and Triple A. In 55 1/3 innings, he struck out 65, walked 13 and held opponents to a .158 batting average.

“I can’t recall two players who have separated themselves from the rest of the pack any more in back-to-back years in the draft than Strasburg and Harper,’’ Rizzo said.

The Pirates, another franchise suffering tough times, selected hard-throwing Texas high school righthander Jameson Taillon with the second pick. He was considered the top pitcher in the draft.

Baltimore picked smooth-fielding Florida high school shortstop Manny Machado, and Cal State Fullerton shortstop Christian Colon went to the Royals at No. 4.

With the fifth pick, the Indians took Ole Miss lefthander Drew Pomeranz.

Texas A&M righty Barret Loux went sixth to the Diamondbacks, and North Carolina righthander Matt Harvey was selected by the Mets at No. 7. Then the Astros took Georgia high school outfielder Delino DeShields Jr.

Florida high school righty Karsten Whitson went ninth to the Padres, and Texas-Arlington outfielder Michael Choice rounded out the top 10 picks by going to the A’s.

Material from the Associated Press was used in this report.