Nearly a decade later, Richards and the Los Angeles Kings will battle Clarkson and the New Jersey Devils for hockey's ultimate prize during the Stanley Cup Final, which gets under way Wednesday night at Prudential Center (8 p.m. ET; NBC, CBC, RDS).
When Richards and Clarkson collide over the next two weeks, both literally and figuratively, their usual exchange of text messages will take a back seat.
"He's a teammate and friend who I'll speak to when this is over," Clarkson said. "He was someone I played with for quite a while and my captain in junior. But at the end of the day, this is something you dream of. We won't speak till it's over, but he's a heck of a hockey player."
Clarkson isn't too bad himself -- and both he and Richards can credit Devils coach Peter DeBoer for helping get them to the NHL.
Richards and Clarkson were teammates with the Kitchener Rangers from 2002 to 2005, winning a Memorial Cup in their final season together. DeBoer was their coach and formed bonds that are still strong today. Much like Clarkson, DeBoer will put aside his relationship with Richards for a couple weeks.
"He grew up as a player and a young man in the organization I was running in Kitchener," DeBoer said of Richards. "Winning follows him around. We won a Memorial Cup together, we won a World Junior Championship together. He's obviously a special kid. I'm very happy to see what he's done. I'm not surprised. But I also know Mike Richards would run you over with his car to win a Stanley Cup. He'd visit you in the hospital after, so I know what I'm dealing with there.
"I love Richie. We won together and grew up in the organization I was running. He's a great kid. He's one of those guys you want in the foxhole with you if you're going to war. Also, we have some of those guys on our team, too. So it will be a great battle."
Richards joined Kitchener in 2001 as the fourth pick in the 2001 OHL Priority Selection. Clarkson entered the OHL with far less pedigree -- he was selected in the 10th round (No. 203) by the Belleville Bulls and was traded to Kitchener during the 2002-03 season.
When DeBoer first got to know Clarkson, he was rough around the edges. When DeBoer was asked how much maturing Clarkson has done since that time, he replied, "Oh, a lot."
"When I had Clarkie, he was a 17-year-old kid who had a lot of growing up to do," DeBoer continued. "He's a man now, a husband, a father and he's an NHL pro. His mental game and maturity, he's a totally different player and person. It's been fun to see him kind of morph into that."
Clarkson had a laugh when told what DeBoer thought about his maturity level as a teen, but agreed he received some much-needed help in terms of developing as a player and a person.
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"When I was younger, I liked to fight a little bit," said Clarkson, who had 485 penalty minutes in 185 career games in the OHL. "There were times during games when he didn't want me to do stuff, and I'd do it. That was just the way I was. I think he learned to teach me a time and a place. I think that was one of the big things he taught me, when to go out and fight and or stick up for a teammate and when to do something. The coaching staff in Kitchener helped me mature as a player. He's definitely helped me quite a bit."
Richards had to do some maturing of his own, but it was less about when to drop the gloves and more about learning structure in Kitchener, something that he said translated into a quick adjustment in the NHL.
"He taught me to be a professional, and that's what he did in junior," Richards said. "He ran things very strict and like you'd expect when you got to the NHL if you did. That four years (in Kitchener), he taught me a lot. He's probably one of the guys who taught me the most in a game, in a sense, coaching-wise."
Clarkson was able to continue his education this season under DeBoer, who was named coach of the Devils last summer. The 28-year-old seemed to be on the rise during his previous three seasons, going from 17 goals in 82 games, to 11 goals in 46 games, but then he dipped to 12 goals in 82 games last season as the Devils missed the playoffs.
When DeBoer arrived, seemingly so did Clarkson's confidence. The right wing scored a career-high 30 goals this season while playing about 16 minutes per game and seeing steady time on the power play. That wasn't the case last season, when Clarkson saw about 13 minutes of ice time and had about half as much time on the power play as he did this season.
DeBoer's up-tempo style and obvious faith meant everything to Clarkson, who went undrafted and signed with New Jersey as a free agent.
"He believed in me," Clarkson said. "He saw things in me that he felt he could help me become. … I don't know if he could tell you he thought I'd be here, but I think he believed in me. I always dreamed of playing in the NHL, but I never knew I would get here. But to be sitting here today is pretty special. I think he's a big part of why I'm here. He pushed me in the right direction as a young kid. I think he's really helped me get to where I am.
"Getting that extra ice time, he believes in me, he puts me out there in all situations. There's a structure in place that he asked to play. I was used to some of the things he had brought in, he did a lot of the same things in junior. I think that helped a ton, but I think just giving me an opportunity, giving me a chance to get on those extra minutes. It's been fun."
Follow Dave Lozo on Twitter: @DaveLozo