Down 7-5, Bryce Harper vowed to teammate Brandon Crawford to hit a game-winning home run.
"I'll drop a bomb and walk off the field, tell them we own this place," Harper said. "I promise you I'm going to hit a jack right here. I swear on everything."
"Yeah, OK," Mike Trout told him in disbelief.
Trout led off with a single, Scottsdale got another hit with one out and Harper followed with a home run to right-centre off Jeff Inman.
"Everybody ran inside the clubhouse," Harper said. "It was a great moment."
Still tied together, baseball's youthful dynamic duo will be watched by millions on Tuesday night as the All-Star game returns to Kansas City and beautiful Kauffman Stadium for the first time since 1973.
Just 19, Harper is the youngest position player in All-Star history and a key part of the Washington Nationals' emergence as a first-place team. Trout, a year older, is leading the American League in hitting and helping the Los Angeles Angels turn around their season after a sloppy start.
Coincidentally, both came up to the majors leagues on April 28, Harper for his debut and Trout for his return following a pair of stints last year. They are among a record five rookie All-Stars, joined by Texas pitcher Yu Darvish, Oakland closer Ryan Cook and Arizona pitcher Wade Miley.
In a room full of baseball's best, even the veterans are taking notice of Harper and Trout.
"Speed. Power. Excitement. Youth. Energy," Yankees centre fielder Curtis Granderson said. "If they are able to stay healthy, they can completely transform the game as they get, five, 10, 15 years of big league time."
For now, both will start Tuesday night's game on the bench.
With the result determining home-field advantage in the World Series for the 10th straight year, the AL manager Ron Washington will start reigning MVP and Cy Young Award winner Justin Verlander. The NL's Tony La Russa, the first inactive All-Star manager since the AL's Bob Lemon in 1979, chose San Francisco's Matt Cain — coming off a perfect game last month — over knuckleballer R.A. Dickey of the New York Mets.
Trout was on a flight from Salt Lake City to Cleveland when he saw on Twitter that Harper was being called up the same day. Trout hadn't let many people know he was joining the big league team.
"Knowing he was getting called up that same day was pretty funny," Trout said.
A son of former Minnesota minor league infielder Jeff Trout, Mike was taken by the Angels with the 25th pick on the first round of the 2009 amateur draft. Idolizing Derek Jeter, he played shortstop at Millville Senior High in New Jersey until he was moved to the outfield in his senior year. He understands why he lasted so late in the first round.
"A lot of risk. East Coast kid. Didn't play all year," he said. "You look at the teams in Florida and California, they've got perfect weather all year. They can play all year."
Harper had the greater renown, on the cover of Sports Illustrated when he was just 16 with the headline "CHOSEN ONE." With sunglasses hanging from the top of his shirt and a neatly cropped beard, he has the big league look. A hint of acne reveals he's still a teenager.
"So much pressure — no, I'm just kidding," he said, joshing with the media.
Joining a Nationals team that already has a top youthful star in ace pitcher Stephen Strasburg, Harper has a .282 batting average with eight homers and 25 RBIs in 63 games. The only younger All-Stars were Bob Feller in 1938 and Dwight Gooden in 1984, both closer to their 19th birthdays than Harper.
"I still feel like I have that kid inside me that wants to play the game of baseball every single day," Harper said. "I got love and that passion for the game and, hopefully, I can keep it going. I hope I'll be able to play for the Nationals for a long time and be able to play in the big leagues for a long time because that's the dream."
While Harper is polished following years of interviews, Trout projects a golly-gee demeanour, with close-cropped hair and a beaming smile. After he twice crashed into the centre-field fence at Denver's Coors Field last month, teammates Jered Weaver and Dan Haren suggested he turn down the enthusiasm by a few notches.
"It's a long year. We're going to need you," Trout remembered them telling him.
He's hitting .341 with 12 homers, 40 RBIs and 26 steals in 29 chances.
"I was just telling Jete, I've never seen a player hit a triple to left field, down the line," Yankees ace CC Sabathia said. "Raul (Ibanez) plays it off the wall, and he's standing on third. That's just fun to see. What he's doing is amazing."
While Trout was an All-Star shoo-in, La Russa appeared reluctant to select Harper and added him on Saturday as a replacement when Miami's Giancarlo Stanton got hurt.
Even the 67-year-old La Russa, who managed his first World Series champions before they were born, appreciates the focus on the new stars.
"It would be nice to put the National League phenom against the American League phenom," he said.
When discussing Trout, Harper sounds like a fan.
"He's fun to watch. I get pumped to watch him," Harper said.
They hope this is just the first of many All-Star appearances. For every Willie Mays, who played his 24th and final All-Star game in Kansas City, there is a Gooden, who was selected in four of his first five seasons and then flamed out because of injuries and drug use.
Harper and Trout know what they can become. They are the next generation, playing alongside the present.
"I think certain guys who have been introduced to the game of baseball early on in life," said 40-year-old Chipper Jones, who is retiring at the end of the season. "Travel ball has accelerated so much for the development of young players these days. Back when I played, we played 30 games a year, and I'd move on to football and basketball, and run a little track."
Yes, much has changed. But much is the same.
Harper wants to become just like Jones, a perennial All-Star respected by his peers.
"Any time I can do that and be that guy that's the face of baseball, I think that would be great, to be able to do that, to be able to play the game for a long time and respect everybody around me and respect the league," he said. "That would be a lot of fun."
NOTES: Detroit's Prince Fielder became only the second player to win multiple titles in the Home Run Derby, thrilling a crowd of 40,351 with eight splash shots into the right-field fountain and beating Toronto's Jose Bautista 12-7 in the final round. Ken Griffey Jr. won it three times.