It all began when Diaz, a single mother since her only child was 4 years old, took Perez to a baseball school in the industrial hub of Valencia, a city of more than 1.5 million.
"I never even dreamed of this," Diaz said in Spanish through a translator. "I didn't take him because I wanted him to be a professional player -- all I wanted was for him to keep busy in his spare time and stay away from bad influences. So it was a big surprise to me when he was 12 or 13 years old and I started hearing from his coaches that he was going to become a pro, that he has the makings of a Major Leaguer."
By the time Perez was 6, his talents for throwing, catching and hitting a ball were being recognized. He was selected for teams that went to state and national tournaments, sometimes as a pitcher or shortstop.
Perez's mother, who made her first visit from Venezuela to Kansas City for the Royals' final homestand, remembered how he became a catcher. When he was 8 years old, coaches were forming teams and told kids to line up at whatever position they wanted to play. To his mother's astonishment, Perez walked to the line -- a very short line -- for catchers.
"You have never played catcher," Diaz remembered telling Perez. "He said, 'Yes, but did you look at the lines? You don't see that many kids in the catchers' line. I want to be a catcher.'"
That was an early indication of Perez's independence and leadership.
"If I saw everybody was wearing blue shirts, I'd wear a red shirt," Perez said.
Perez decided at about age 14 that catching would be his future, and by the time he was 16, the Royals agreed and signed him to a contract on Sept. 27, 2006. He played in 2007 for the Rookie League team at Surprise, Ariz., and four years later, he was playing in Kansas City.
When the Royals left for Chicago and Minnesota for their final six games of the season, Perez's Major League career was 33 games young and he was batting .344 (43-for-125). He was on a roll, too, having hit in 12 of his last 13 games at a .460 (23-for-50) clip.
Perez's first game in the Majors -- he was unexpectedly called up on Aug. 10 at Tampa Bay -- proved to be a showcase for his defensive skills. He picked off two runners, the first all season for the Royals, and caught five popups, another rarity. He also got his first hit, a single.
Manager Ned Yost had been impressed by Perez's arm and quick release as well as his ability to block balls in Spring Training. His game-calling insight also became quickly evident.
"He's really good -- he picks things up really quick," Yost said of Perez. "He's very, very good, a quick learner. In all aspects of it -- learning the pitchers, what they like to do, learning the opposition -- he's done a nice job. I'm very pleased."
Perez's ability to adapt to his own pitchers and analyze opposing batters was enhanced by use of videos on an iPad, a gift from veteran pitcher Bruce Chen. After Tuesday's win over Detroit, Perez turned on the iPad and showed a video he'd studied of a Tigers batter missing a pitch earlier in the season.
"You have to see this -- this helped me a lot," Perez said, pointing to the screen. "This is why we got a strikeout on him, because I knew he was bad on breaking balls."
"All I wanted was for him to keep busy in his spare time and stay away from bad influences."
-- Yilda Diaz, mother of Salvador Perez
Perez's success in hitting, he feels, is mostly a result of persistence in the batting cages. After a marked improvement last year at the Double-A level, the Royals' staff was convinced that Perez would hit.
"Did I think he'd hit .300? No," Yost said, "but I knew he'd hit."
Perez has power -- his first home run, on Aug. 29, was a 415-foot whopper -- and he doesn't strike out much, just 17 times in 134 plate appearances so far. Constant contact helps him accumulate some flip hits and dunkers.
"That's what you do when you don't strike out," Yost said. "When you don't swing and miss at a high rate, you put the ball in play, and he's got that ability to almost give you an emergency swing, where you stand and just, boom, foul it off. That's another reason he'll hit."
Well, really, it was probably all of those corn kernels Perez hit off mom's pitching.
At that suggestion, Perez's face lights up and he breaks out in a deep, joyous laugh that can shake a room.
"My mom is my support," Perez said. "She has been with me every step of the way. She is not just my mother, she is my friend and my helper. And don't forget -- my grandmother is the very same thing."
During the season, he calls his mother in Venezuela twice a day. While she was visiting Kansas City, they called his grandmother twice a day.
When Perez was about 8, he and Diaz moved in with her mother, Carmen de Diaz, in Valencia. He was raised with plenty of love and as many arepas, those round cornmeal Venezuelan delights, as he could eat. To this day, his grandmother dotes on "Johan," his middle name, and serves up arepas filled with eggs, cheese or meat as big and round, he says, as "the size of a CD."
Cooking runs in the family. Yilda supported the family by arising at 5 a.m. to prepare lasagna, cakes and flan, which she sold out of her home or out of friends' car trunks at young Salvador's baseball games. She built up quite a clientele and still sells the cakes and flan on order.
"I worked hard so he could go to school and play baseball," Yilda said.
The industrious mother, in addition to selling food between innings, also found time to act as a "front-office official" for her son's teams, handling the paperwork, assembling the equipment and attending league or tournament meetings.
In turn, Perez -- while not a perfect angel -- was, in his mother's words, "obedient and respectful," although she does remember an exception from his high school days.
"One time, he had an eraser and threw it at the door and, at that moment, the teacher opened the door and it went, zoom, right over her head," Diaz said. "It didn't hit her, but it came close."
The teacher was not amused, and she was reluctant to give Perez the honors pin he earned that year as an outstanding scholar. In the end, she relented; Perez got his pin and the teacher got a hug from the relieved student.
Heck, Perez was probably just using the eraser to practice his throws to second base. If so, it was worth the effort.
The signing bonus that Perez received from the Royals was turned over to his mother for the purchase of a house for her, Perez's grandmother and himself. It was the catcher's way of saying thank you for their love and devotion.
"There was enough left over that we could help some people who needed it," Perez said.
Yost sees the effects of Perez's upbringing in his demeanor at the ballpark.
"He's great natured, has a lot of energy, a happy guy -- I never see him pouting or complaining," Yost said. "He's got a perfect disposition and constitution."
Here's something that Yost might not know. The quick feet that his 6-foot-3 catcher has shown behind the plate might have started at a very young age as well.
"Salvador loves dancing," Diaz revealed. "When we have a party, I know I'm going to be dancing, because Salvador loves to dance. Salsa, merengue, reggaeton -- he has loved dancing since he was a little boy."
Perez's mother has saved mementos of her son's life in baseball.
"I have the first spikes he ever used when he was 4 1/2 years old -- the first glove he ever used," Diaz said. "The first jersey that he ever wore at 4 1/2 was No. 13, so I'm thrilled he is wearing it as a Major Leaguer. And I believe that in baseball, No. 13 is a lucky number."
Lucky, the Royals hope, for many years to come.