A game-changer he was. Harper, at age 19, was in the big leagues by the end of April and earned National League Rookie of the Year honors as he helped Washington to a National League East title. And he was far from the only player absent from Opening Day to make his presence felt in 2012.
Every year, much emphasis is placed on which players will break camp with their Major League clubs and participate in the pageantry of the season opener. But for those who fell short of the goal this year -- for reasons other than injury -- last season should provide plenty of hope and inspiration. From young phenoms such as Harper and Mike Trout to journeymen such as Miguel Gonzalez and Brandon Moss, numerous players overcame the initial setback to establish themselves and impact pennant races.
That sort of productive response isn't something everyone can manage, so front offices must agonize over every possible consequence of a demotion.
"Every situation and scenario is different," Nationals general manager Mike Rizzo said. "There are some guys who are going back to Triple-A, who have been to the big leagues, and that's a different scenario than a guy who is up-and-coming going to Triple-A. You have to take every situation independently and weigh the positives and negatives that can occur from sending them down to the Minor Leagues."
With Harper, Trout and other top prospects, there are off-the-field considerations. Waiting past Opening Day for a callup can delay how quickly a player reaches eligibility for arbitration and free agency.
But there also might be concerns about a prospect's readiness for Major League competition, no matter the talent level or Spring Training success. Even after watching Harper hit .270/.340/.477 with 22 home runs, perhaps the finest season ever produced by a teenager, Rizzo saw validation, rather than a reason to second-guess.
"Well, I think it was a great decision," Rizzo said last week amidst Harper's hot start, during which he hit three homers and had five RBIs in the Nats' first five games. "I thought he needed some extra at-bats. He had never played at the high Minor League level, and I thought that was valuable experience to figure out that level. The pitching at that level is much different than it is at the low [Class] A levels, and it gets you much more prepared for a Major League season."
Regardless of whether the early Minor League time served as necessary seasoning or a superfluous delay, several prospects flourished when eventually called upon.
Trout won the American League Rookie of the Year award and finished second in the AL Most Valuable Player voting despite not playing his first game until April 28. Reds third baseman Todd Frazier helped his club to an NL Central title by racking up 19 home runs and an .829 OPS. Cubs first baseman Anthony Rizzo forced his way to the big leagues by hitting .342 with 23 homers in 70 games at Triple-A Iowa, then hit .285 with 15 dingers in 87 games for Chicago. A's pitcher Jarrod Parker won 13 games and had a 3.47 ERA.
Mets pitcher Matt Harvey, Orioles third baseman Manny Machado, Red Sox third baseman Will Middlebrooks and Braves shortstop Andrelton Simmons were some of the other rookies whose strong play last year cemented their spots on 2013 Opening Day rosters.
Among the top prospects who could seize an opportunity sometime this season are pitchers Dylan Bundy and Kevin Gausman of the Orioles, infielders Nolan Arenado of the Rockies and Jurickson Profar of the Rangers, outfielders Billy Hamilton of the Reds and Oscar Taveras of the Cardinals, and catchers Travis d'Arnaud of the Mets and Mike Zunino of the Mariners.
On the other hand, many of those squeezed off Opening Day rosters are older players looking to break through or get a long-awaited first chance. Their contributions also can be significant, if less anticipated.
The Orioles' Gonzalez, for example, has shown how much things can change in a year. He was in Minor League Spring Training in 2012, but got a shot with Baltimore after a hot start at Triple-A and wound up going 9-4 with a 3.25 ERA to help the O's capture an AL Wild Card spot. On Opening Day 2013, he lined up for introductions during ceremonies before the Orioles took on the Rays at Tropicana Field.
"It's incredible," Gonzalez said. "I think things happen for a reason. Last year I was nowhere to be found, and this year they gave me a chance to be the third starter."
Moss was one of several A's, along with Parker, who spurred the team to an AL West crown despite not being among its original 25 players. Oakland became Moss' fourth club in six years when he arrived from Triple-A Sacramento in early June, and he led the A's with a .954 OPS and finished third on the team with 21 homers.
Others, such as Twins pitcher Scott Diamond, Phillies infielder Kevin Frandsen and Marlins outfielder Justin Ruggiano, also took advantage when given a chance.
Unexpected contributors are sure to emerge this year as well, perhaps along with some veterans searching for another shot. Consider Blue Jays pitcher Ricky Romero, who won 15 games with a 2.92 ERA in 2011 but is starting this season at Class A Advanced Dunedin following a rough 2012. Or Jose Valverde, who could reclaim the Tigers' closer role after returning to the club on a Minor League deal last week.
While the wait is no doubt difficult, patience could pay off for the likes of Nationals pitcher Chris Young, 33, who will begin his season at Triple-A Syracuse but might be the first option should Washington need a starter.
"He's a qualified, quality Major League starting pitcher," Rizzo said. "He's a guy who could help us down the road."