The 38-year-old has been involved with youth baseball clinics and lessons for years, but this marks his first year with RBI, in which he's helped lead the White Sox club to this week's World Series.
"I played [the game] 15 years. I love teaching it," Collier said. "I talked to [head coach] Kevin [Coe] and said, 'Hey man, I need to come out and coach with you.'"
Collier certainly isn't short on credentials. He starred for Chicago's Vocational High School before playing at Kishwaukee Junior College and Triton Community College, where he was named the National Junior College Player of the Year before signing with the Pirates in 1993.
He played eight big league seasons for the Pirates, Brewers, Expos, Red Sox and Phillies. But Collier said he always looked forward to coaching opportunities, too.
"I always wanted to do it," he said. "Even when I played, I always had that in the back of my mind. When I retired, I wanted to come back and start coaching young kids and teach them what I know."
Coe -- a former Minor League player and draftee of the Cubs in 1994 -- said he's been able to work almost seamlessly with Collier, who he met back in his playing days.
"For him to be around the kids, take his big league experience and share it with the kids and tell them what they need to do, it's second to none," Coe said. "For him to come back and work with RBI kids is even that much better. He's a really, really good guy. He wants to see the kids get better. He's a great instructor, he knows how to communicate."
With round-robin play beginning on Thursday, Collier and Coe lead a squad that is particularly hungry for a championship. The White Sox senior team includes multiple players from last year's junior team that came a game shy of reaching the Junior Division Championship.
But Collier is making sure a title isn't the only thing his players are focused on.
"I tell them all the time, 'You're getting a big league experience [being at the RBI World Series].' Seventeen years old," Collier said. "You're supposed to earn that. But these kids have earned it. They've worked very hard to be where they're at. I tell them every day they wouldn't be here if they didn't deserve it. They're enjoying this opportunity and they're not taking it for granted -- I won't let them."