"He's definitely one of the main reasons why I made it to the big leagues," David Eckstein said. "I was set off track at one point in my career with some bad advice, and if I didn't have him, I probably never would have gotten out of that.
"He knows my swing better than anybody else."
The collaboration between the brothers has certainly worked.
David has a .282 lifetime batting average and is a former World Series MVP in 2006. He has been the most consistent hitter for the Padres this season, leading the team in average (.293) and doubles (13) while also recording the fewest strikeouts among everyday position players (five).
"He understands who he is and his role," Rick said. "He's never been a power hitter. David, from a very young age, realized, 'I'm a guy who's going to hit singles, and if I get a good pitch to hit, I can drive it into a gap.' He's hit a few home runs in his career, but his mind-set is, 'I'm going to go up there and deliver an at-bat that's going to make the pitcher work.'"
David and Rick's relationship remains close off the field as well. Rick stayed at David's house during the three-game series in San Diego this week, and David's entire family made the trip to Washington, D.C., when the Padres played the Nationals there last season.
"David's been my best friend my whole life," Rick said. "We've always been really, really close, and the game of baseball, I think, attributed to us being even closer."
Even though Rick now teaches hitting for a living, he wasn't a natural with the bat like David when they were youngsters.
"I always knew how to hit. Rick didn't," David said. "My dad would yell at him, 'Why can't you just hit like [David]' growing up."
But while in junior college, Rick was told he needed to learn how to hit left-handed or he wouldn't play. So Rick taught himself to switch-hit, which sparked a "fascination" with learning how each individual player uniquely handles a bat.
"With any hitter that I've ever worked with, I try to explain to them what they do and how they do it and what position that is and how their body works best," Rick said. "I really try to make a hitter understand himself, in a nutshell. Once the hitter knows himself, the plan and everything starts to come together."
In Rick's first season in Washington, he helped the Nationals hit .258 as a team and rank second in the National League with 617 walks. This season, Washington ranks 14th in the NL with a .259 average.
"There's no surprise what [the Nationals are] doing offensively, because I know what [Rick] can do," David said. "As long as the guys trust in him, they'll have success, and I promise you that."
And for Rick, the long-term offensive success of his brother and first pupil also isn't a surprise.
"Growing up with him, you just knew there was something very special about him," Rick said. "But to see him go out there and compete and the respect that he receives from his teammates and the coaches around the league, it just puts a smile on my face every day."