It was his father, Nelson Cruz, Sr., who pounded one basic message into his son.
"I teach my students to be right," the father told the son on more than one occasion. "If I can't teach my son to do the right things, how am I supposed to teach my students?"
Cruz received the message loud and clear as he grew up in the Dominican town of Las Matas de Santa Cruz in a tight-knit family that included his mother, Dominga, and two sisters, Nelsy and Olga.
"[My father] taught me to respect people and treat people the right way," Cruz said. "No matter what I think of people, you always treat people the right way and you treat them with respect. Everything I know from a life perspective, I learned from him. He was my teacher, so I had to stay on the straight and narrow."
That's why Cruz worked so much growing up. He was 9 years old when he first started helping in an auto repair shop fetching tools for the mechanics.
"He told me, 'You've got to be tough. Things are not going to come easy and they're not always going to come your way,'" Cruz said. "Before, I used to think he was mean. Now I realize he was trying to make me a good person. Now when I talk to kids, I tell them to respect their parents because they're trying to teach you to do things the right way.
"The main thing he used to tell me was, 'You have to go to school and you have to learn. You have to do good in school. You can't have bad grades.' Trust me, since he was my teacher, he had a chance to check the books. If I had bad grades, he knew. I always did my homework."
Cruz's father taught history. He taught his son in ninth, 10th and 11th grades. He taught the history of the Dominican Republic, plus world history and geography. But there was one year that he didn't teach.
"I remember the teachers went on strike," Cruz said. "He had to take other jobs. He had to fix shoes to give us food. He did plumbing stuff and he had to go to the fields. When the rice had grown, they had to ... carry it in bags to the road so the trucks could pick it up.
"He would do anything to provide for us -- my mom, me and my two sisters. We didn't have toys but we had what we needed to survive: education, food and a house. Even after the strike was over, my dad kept doing those other jobs because they made more money. He would teach in the morning and then go fix shoes after school."
His son started working at a young age as well.
"It wasn't to earn money," Cruz said. "He said if I kept myself busy doing other stuff, I wouldn't get into trouble. He taught me that hard work was good for you. When I was a kid, I was always working."
Of course, he also played baseball. His father played professionally in the Dominican, loved to play softball and loved to play catch with his son. Cruz also played basketball and was good enough to play for the Dominican Republic Junior National team.
But he finally decided on a baseball career and signed with the Mets on Feb. 23, 1998. After he signed, he was looking forward to playing in a basketball tournament that week in his hometown.
His father put a stop to that.
"My dad told me I was quitting basketball," Cruz said. "He said I had given my word to play baseball and I was going to live up to my word. He didn't want me to get hurt playing basketball. We got into a 'discussion.' Well, there was no discussion. When he said something, he meant it.
"My family means everything; my mom, my dad, my two sisters. When I was having tough times early in my career, I don't think I could have gone through that without their help and support. My dad, he didn't say this to me at the time, but he was telling other people, 'My son knows how to work and work hard. He is going to work through this.'"
At the end of Spring Training in 2008, the Rangers designated Cruz for assignment so they could send him to the Minor Leagues. Any team could have picked him up for nothing. Nobody did.
In 2009, Cruz was selected to the American League All-Star Team. One year later, he was playing in the World Series. And in 2011, he was the Most Valuable Player of the AL Championship Series after setting a playoff-series record with six home runs and 13 RBIs.
In the Cruz family, father did know best.