WASHINGTON -- Juan Soto just keeps hitting home runs.

Making his first start for the Washington Nationals on Monday, the 19-year-old outfielder went deep in his first at-bat against Padres starter Robbie Erlin, helping propel Washington to a 10-2 win over San Diego. Soto's three-run, opposite-field shot came on the first pitch from Erlin and traveled an estimated 422 feet before landing over the wall in left-center.

"I didn't think it was going to go out of the park," Soto said. "I just run hard, the same I do in the minor leagues. Then I heard the noise, and I know it was gone."

Upon returning to the dugout, Soto received a curtain call from the crowd at Nationals Park.

Before getting called up this past weekend, Soto was hitting .362 with 14 homers in 39 minor league games across three levels. Despite those numbers, his promotion was a surprise, given that he had only 31 at-bats above Class A. But after utility man Howie Kendrick tore his Achilles on Saturday, the latest in a rash of injuries that has severely depleted Washington's outfield options, Soto got the call, making him the youngest player in the majors.

Nationals left fielder Juan Soto hit a three-run homer in the second inning against the Padres on Monday. Brad Mills-USA TODAY Sports

His ascent to the bigs was so sudden that, as of Monday, he didn't have a name plate at the top of his locker.

That wasn't the only thing that stood out. While taking batting practice before his first start, Soto was the only member of the Nationals wearing a helmet, a choice he made expressly for the purpose of getting accustomed to the single-flap ear helmet worn in the majors instead of the dual-flap model he used in the minors. By the time first pitch rolled around, he seemed more than comfortable.

In addition to his second-inning homer, Soto singled in the sixth and came around to score on a Michael A. Taylor triple. In his other two plate appearances, he grounded out to shortstop and lined out to right field, both times putting the ball in play with two strikes.

Afterward, Soto's teammates sang his praises.

"He's a special player," said Bryce Harper, who hit his NL-leading 14th home run on Monday and who, before Soto, was the last MLB player to homer as a teenager (Sept. 30, 2012). "We've seen that throughout the minor leagues, and we saw that in spring training as well. So we're all just excited for him to be here and excited for him to help us out and super proud of him and just got to keep it going."

"It's unbelievable to be 19," said veteran first baseman Mark Reynolds, who went deep twice for his second multihomer effort in six games since being called up. "When I was 19, I could barely swing a metal bat. So it's pretty impressive, and I'm glad he's here."

So are the Nationals. Besides Kendrick, the Nationals have dealt with injuries to starting left fielder Adam Eaton (ankle), reserve outfielder Brian Goodwin (wrist) and outfield prospects Victor Robles (elbow) and Rafael Bautista (knee).

At 19 years, 208 days old, Soto became the youngest big leaguer to hit a home run since the Texas Rangers' Jurickson Profar homered on Sept. 2, 2012. At the time, Profar was 19 years, 195 days old. Soto is the youngest player in Nationals/Expos franchise history to hit a home run.

A native of the Dominican Republic, Soto signed with Washington in 2015 for a reported $1.5 million. Entering the 2018 season, he was ranked as the Nationals' second-best prospect and No. 42 overall by ESPN's Keith Law.