At every opportunity he had, Molina looked on in awe, yes, but also with intent to absorb.
"The way he caught, the way he held himself, I always looked forward to working with him," Molina recalled on Saturday, one day before the Cardinals begin the National League Championship Series against the Giants. "I was in the cage watching him do the drills and everything. At that time, I was just learning. I knew how hard he worked and how good he was."
Funny thing was, Matheny thought the same of the budding young prospect. He saw in Molina receptiveness to learn and to improve and to grow. He saw a work ethic matched by few his age.
And so it was after one Spring Training workout that Matheny returned home and broke the news to his wife, Kristin.
"I saw the kid," Matheny began, "that's going to steal my job."
It took a few years, loads of instrumental instruction from coach Dave Ricketts and an opening when Matheny went on the disabled list with a strained rib cage in 2004, but Molina did arrive. And not long after, he pushed his now-manager out of a starting job.
It was evident early that the youngest of the three Molina brothers would become the most accomplished. His defensive ability was above-average, his game-calling evolved with ease.
In 2008, Molina won his first Gold Glove Award. He's taken home the annual honor each season since and added the inaugural Platinum Glove -- given to the league's best defensive player regardless of position -- to his award case in 2011.
Yet, as backup catcher Tony Cruz maintains: "It's so much more than what people see on the field as far as his blocking and his good arm. It's that leader aspect, I think, that he carries. It's obvious that his ability is way up there. But it's the passion and that drive that he has to want to be the best. I don't think anyone outworks him. He strives to be the best and he puts in the work to do it."
Few have more of an appreciation for that than the pitchers, all of whom are made better by Molina's presence.
This year, the staff posted a 3.60 ERA with Molina behind the plate. That ERA rose to 4.15 when anyone else was catching. He threw out 47.9 percent of attempted basestealers, though that number can't accurately reflect how many he stopped by making them hesitant to start.
Young pitchers are told never to shake him off. And when they mature, they usually still don't.
"You could talk all day about how special Yadi is," said starter Adam Wainwright. "I think the big thing is that he gives you confidence in many different ways. You know you can bounce balls. You know you can throw balls to the corners and he's going to make them look like strikes. He's going to throw guys out. He makes you believe in your stuff the way he talks to you on the mound."
"He does a great job of studying hitters along with us, knowing our pitchers, our strengths," added Kyle Lohse. "I don't have to worry about him just calling pitches, not, you know, paying attention to what's going on in the game. He's very smart and does a great job back there."
Molina's defensive impact has been steady; his offensive production, however, has taken off.
Though he hit for average from the get-go, Molina's power production has evolved. Matheny credits Albert Pujols' tutelage. Molina asserts that third-base coach Jose Oquendo was influential as well. With the two, Molina developed a more focused approach.
"[Pujols] would talk about how to know the pitchers, and he showed me how to study the pitchers," Molina said. "I've been fortunate to have those guys when I started over here. Right now, I'm practicing what they taught me."
The payoff has been substantial.
Molina had never hit more than eight home runs in a season until 2011, when he connected for 14. This year, Molina finished with 22, a total surpassed by only two other catchers in the league.
He drove in a career-best 76 runs, hit a career-high .315 and stole more bases (12) than any other National League backstop. He became a fixture batting fifth in a St. Louis lineup loaded with heavy hitters. And after hitting .305 last year, Molina became the first catcher in franchise history to lead the team in batting average for consecutive seasons.
"I want to be the best at that position, and I work physically and mentally so hard to be good in all aspects," Molina said. "I just want to be the best that I can. You have to think that way. If you get comfortable, you won't be here for a long time. You can't be comfortable in this game. You have to constantly work to get better."
Having made his game more complete, Molina, for the first time in his career, became a serious Most Valuable Player Award candidate in 2012. Perhaps his steepest competition will be the catcher he'll be helping his pitchers stop for the next week, Buster Posey.
Matheny, while biased by his position, doesn't see the debate as so blurry. As certain as he was a decade ago when watching a young 20-something catcher develop his skills, Matheny is equally as certain in what Molina has evolved into since.
"I will stand behind the fact that Yadier Molina has impressed me more than any catcher I've ever witnessed," Matheny said. "Yadi had a lot of people investing into him with his family and people from the outside, but he had to do it himself. He had to take what he was given and make the most of it, and he continues to get better.
"I don't know that we've seen the best of him," Matheny added. "I think there's even more there. He's special."