The Washington Nationals recalled Bryce Harper from Class AAA Syracuse on Friday after placing third baseman Ryan Zimmerman on the 15-day disabled list with right shoulder inflammation, promoting the first overall pick of the 2010 draft to the majors five months before his 20th birthday.

Harper will make his major league debut Saturday at Dodger Stadium, a call-up that came faster than Harper or the Nationals anticipated and necessitated by injuries.

General Manager Mike Rizzo made his bones in player development, and he crafted a careful scheme for Harper’s ascension, which included 250 to 300 at-bats at Class AAA Syracuse. But with left fielder Michael Morse out until midseason, Zimmerman also sidelined and punchless bats currently occupying left field, Rizzo traveled to Rochester, N.Y., this week to personally scout Harper. After watching him play left field for three days, Rizzo decided Harper — 72 at-bats into his Class AAA career — would come to the majors, ready or not.

“The decision is really a team decision,” Rizzo said. “It’s to support the major league club when we need an offensive player to play corner outfield. . . . This wasn’t the coming-out party for Bryce that we had in mind. This wasn’t the development plan we had in mind.”

Harper will bat seventh Saturday and play left field behind starting pitcher Stephen Strasburg, the 2009 first overall pick who has blossomed, at 23, into the Nationals’ ace. Will Harper play every day?

“Yes,” Manager Davey Johnson said. “As far as I’m concerned, he’s earned the right to have the opportunity. He fits what we’re looking for. A good player coming up to the big leagues is the way I look at it.”

The Nationals made the final decision Friday afternoon, after Zimmerman visited a doctor in Los Angeles who confirmed that the third baseman needed to rest the inflamed AC joint in his right shoulder. The Nationals expect Zimmerman to return May 6, the first day he is eligible to come off the disabled list.

Rizzo followed the usual protocol for informing a first-time big leaguer he had made it. He told Director of Player Development Doug Harris, who relayed the news to Syracuse Manager Tony Beasley. Beasley called Harper into his office and told him he would become the youngest player in the major leagues.

“He didn’t say a lot,” Beasley said in a telephone conversation. “I think he was kind of speechless. We just talked a little bit. Gave him some advice. He was just kind of taking it all in. He was very grateful and humble at the same time. It’s a big day for the whole organization.

“I don’t think he anticipated it,” Beasley added. “None of us did at this point. This is something he’s wanted to achieve for basically his whole life.”

Rizzo left the decision of how much Harper will play to Johnson, who advocated for Harper to make the major league roster out of spring training. But “we didn’t bring Bryce up there to sit on the bench,” Rizzo said.

The move to call up Harper now represents a shift for the Nationals, who started the season 14-5. When they wallowed at the bottom of the standings, they focused on development first and only. Winning has now taken precedence, even when it comes to Harper.