"We played on the same team since we were seven years old through high school," Dominguez said. "We're still good friends and keep in touch. I'll be a groomsman in his wedding this offseason."
Both were drafted in the first round of the 2007 Draft, with Moustakas going second to the Royals and the Marlins nabbing Dominguez with the 12th pick.
They are one of six pairs of high school teammates to be drafted in the first round of the same draft.
The duo led Chatsworth to a 124-11 record, four league titles and two city championships during their four seasons at the school. Moustakas' 52 career home runs remain a California prep record.
But, according to Moustakas, Dominguez always flashed the superior glove.
"I knew he was going to be a Major League player since he was a freshman [in high school]," Moustakas said. "When his stick comes around, he's going to be awesome."
Dominguez's bat has indeed come around lately. He had four home runs in nine games before a quad injury limited him in Tuesday's game. The quad issue also kept him out of tonight's series finale.
Moustakas broke out of his own 0-for-18 slump Tuesday with a game-tying RBI single in the seventh inning as the Royals eventually won 7-3.
Dominguez said the two friends went out briefly after the game and caught up.
"It's good to see him and share this moment together, playing against each other in the big leagues," Dominguez said. "It was a tough loss for us, but he was struggling and you always like to see your friends do well. It's bittersweet."
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. Chris Abshire is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.