But while they have rarely done it in-game, Barmes and Mercer have worked together all season. The former regular shortstop has turned over to Mercer more than his position -- he's given him his expertise and support.
"He's grown Jordy up," manager Clint Hurdle summarized.
Hurdle likened Barmes' supporting role to that served by Steve Kerr with the 1993-98 Chicago Bulls.
"He didn't get to play much, but he got to guard Michael Jordan in practice every day," Hurdle said. "Barmes hasn't gotten to play much, but he's tutoring Jordy every day, working with Walker every day. He's challenged those guys to get better."
So, Hurdle was asked, has he been Mercer's Mr. Miyagi?
"Good call," the manager said. "Except he's a little taller. But same haircut."
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.