"I watched him swing a couple of times," Brett said, "and he was swinging so hard. It's a common thing. They want to show people how far they can hit the ball. If you're not going to swing that way during the game, don't swing that way during batting practice."
Brett also understood the swirl of emotions Arenado was dealing with. He's 21 years old and has played just 362 Minor League games. He had never been in an environment similar to the one Kauffman Stadium offered Sunday afternoon, as 40,095 fans showed up for the 2012 SiriusXM All-Star Futures Game.
For one of the first times in their young lives, Major League Baseball's best talent was thrust on a stage that had the look and feel of the real deal. Brett, who managed the U.S. Team to a 17-5 victory over the World Team, said he kept hearing the same thing during the game.
"The adrenaline was flowing today," he said. "These guys were excited, and I think it took them an at-bat or two to calm down."
Brett laughed remembering Tigers prospect Nick Castellanos surveying the biggest crowd he'd never played in front of: "He's telling me, 'Man, this is unbelievable. I've got to calm down.'"
Castellanos must have gotten himself calmed down, because he had three hits and three RBIs and was named the game's Most Valuable Player.
"It was just an awesome environment," Castellanos said. "It's the kind of thing you dream of being part of."
That was the message from every corner of each clubhouse. Players finally got a taste of the thing they've dreamed of.
"I think you take it all in and understand it's OK to be nervous," said Gerrit Cole, the Pirates' top pitching prospect. "The next time you're in a big league atmosphere, it'll be OK."
Bryce Harper played in this game a year ago. So did Will Middlebrooks and Jason Kipnis. Dayan Viciedo was here, too. Now they're all in the Major Leagues, and that's just a start. They're contributing on teams that are in the thick of pennant races.
In all, 17 players from the 2011 SiriusXM All-Star Futures Game are on Major League rosters, or the Major League disabled list.
When the Futures Game began in 1999, it was supposed to be an opportunity to showcase a future generation of players. Lance Berkman played in that first one. So did Alfonso Soriano, Michael Cuddyer and Aramis Ramirez.
As good as they were, they were all two years away from being full-time Major League players. There appears to be a new timetable in place. By the time many players get to the Futures Game, they're on the threshold of the Major Leagues.
Two players invited to this year's game never made it. The Padres called up catcher Yasmani Grandal before he could make it to Kansas City, and the Diamondbacks did the same with pitcher Trevor Bauer.
That's why we're likely to see several of the players from the 2012 even very quickly. Royals outfielder Wil Myers likely will be in the Major Leagues before this Major League season ends.
Rangers shortstop Jurickson Profar appears to be forcing his way onto the big league roster at some position.
Arenado could be playing third base for the Rockies on Opening Day next season.
Braves catcher Christian Bethancourt is one of the game's best prospects at the hardest position to fill. The Mariners are also excited about left-hander Danny Hultzen, who has already been promoted to Triple-A.
Cardinals outfielder Oscar Taveras is another dazzling prospect who is about to give general manager John Mozeliak flexibility in shaping his team in future seasons.
That's also true of Angels second baseman Jean Segura, who could end up at shortstop.
The Futures Game has become a peek into the future, but the future is arriving faster than ever.
"You look around, and know everybody here has a chance to get there," said Billy Hamilton, the Reds' dazzling 21-year-old shortstop who has 104 stolen bases in 82 Minor League games this season. "If I keep working hard, hopefully it'll be me one of these days. It was a great environment. It felt like they were all on our side."
Some fans saw Joe Mauer and David Wright for the first time at the Futures Game. Likewise, Adam Dunn, Ryan Braun, Madison Bumgarner and Matt Cain.
This year's All-Star rosters include 30 players who participated in the Futures Game, including eight of the 2012 first-time All-Stars.
The 2012 Futures Game included the top two picks of 2011 (Pirates right-hander Cole and Hultzen) and the second and third picks of 2010 (Pirates right-hander Jameson Taillon and Orioles shortstop Manny Machado).
"It was an honor to be here," Hultzen said.
The 83rd Major League Baseball All-Star Game will be televised nationally by FOX Sports, in Canada by Rogers Sportsnet and RDS, and worldwide by partners in more than 200 countries via MLB International's independent feed. Pregame ceremonies begin at 7:30 p.m. (EDT)/6:30 p.m. (CDT). ESPN Radio and ESPN Radio Deportes will provide exclusive national radio coverage. MLB Network, MLB.com and Sirius XM also will provide comprehensive All-Star Game coverage.
Fans will also have the opportunity to participate in the official voting for the Ted Williams Most Valuable Player presented by Chevrolet via the 2012 MLB.com All-Star Game MVP Vote during the All-Star Game on MLB.com.
Richard Justice is a columnist for MLB.com. Read his blog, Justice4U. This story was not subject to the approval of Major League Baseball or its clubs.