WASHINGTON -- One of Christian Yelich's favorite baseball memories came as a middle schooler playing in the PONY Baseball and Softball league with his best friends. Back then, Yelich's teammates started calling him "Yeli," a nickname that's stuck with him through the Minor and Major Leagues.
• Players Weekend gear available at MLBShop.com
During MLB's inaugural Players Weekend from Aug. 25-27, Yelich will play with that nickname on the back of his jersey while sharing his passion for baseball with youth players.
Over that weekend, MLB and the MLB Players Association will give a nod to youth baseball, with all players wearing colorful, non-traditional uniforms featuring alternate designs, as well as players donning nicknames on the back of their jerseys and patches on their sleeves to thank someone for helping them advance their careers.
The Marlins' jersey is covered in aqua blue and orange and will be on display during the team's series vs. the Padres at Marlins Park.
"It's fun," Yelich said. "Kids like colors and freedom of expression, and you kind of see guys in the big leagues wear different things than you're used to. It will probably bring more attention to the game that weekend. Our jerseys are crazy looking, very colorful. It will be a fun weekend. I'm looking forward to it."
In addition to wearing different jerseys, players will be allowed to wear uniquely colored and designed spikes, batting gloves, wristbands, compression sleeves, catcher's masks and bats. Players will also don specially designed caps by New ERA and socks from Stance. During pregame workouts and postgames interviews, they'll wear T-shirts highlighting a charity or cause of their choice.
"Some of [the kids] are eventually going to make it to the big leagues, too," Yelich said. "Who knows where the game will be at at that point, with what you're allowed to wear and not allowed to wear. That used to not happen back in the day. It will be a cool couple of days."
All players will wear a patch on each side of their jersey, honoring people who helped them evolve into a Major Leaguer. Yelich, for example, wrote his mom on both patches. Tyler Moore credited his wife and parents.
Moore, who chose "T-Mo" as his nickname after receiving that name in the Minor Leagues, grew up in Mississippi, so a Major League team didn't play around his hometown. That made it more difficult for him to enjoy events like Players Weekend, but also has caused him to be more excited to celebrate with youngsters now.
"It's awesome," Moore said. "It's just showing those kids hopefully a little bit of positivity in their lives. Some of them don't have that. Just them having a good time, the smiles, being able to joke around with them, just in a positive way. So it's fun to see kids and seeing them have fun with this game. Hopefully they'll do it again."
The Pirates and Cardinals will first wear the uniforms Aug. 20 during the MLB Little League Classic in Williamsport, Pa. That game will take place at Bowman Field, home of the Williamsport Crosscutters, a Phillies affiliate in the Class A Short Season New York-Penn League.
Game-worn, Players Weekend jerseys will be auctioned at MLB.com/auctions, with 100% of net proceeds donated to the MLB-MLBPA Youth Development Foundation, a joint effort established in July 2015 by MLB and the MLBPA with an initial commitment of $30 million focused on improving the caliber, effectiveness and availability of amateur baseball and softball programs across the U.S. and Canada.

Here's a list of nicknames that some Marlins are expected to sport on the back of their jerseys on Players Weekend:
• Giancarlo Stanton: "CRUZ"
• Christian Yelich: "YELI"
• Marcell Ozuna: "THE BIG BEAR"
• Dee Gordon: "VARIS STRANGE"
• Ichiro Suzuki: "ICHI"
• Miguel Rojas: "MIGGY RO"
• Dan Straily: "ROJO"
• J.T. Realmuto: "JT"
• Jose Urena: "EL NUEVE"
• Brad Ziegler: "UNICORN"