In 2013, six years after retiring his glove, Hall-of-Fame baseball catcher Mike Piazza decided to invest in an Atlanta-based startup called Company.com.

"[The investment] started with a personal relationship," Piazza says, referring to a member of the business's executive board, whom he first met when their children attended school together.

He was particularly drawn to Company.com because it provides services and resources to help entrepreneurs with the common challenges of running a small business, like processing payments or managing HR. These were the things his father, who founded an auto dealership in the 1960s, had also struggled with: "Because he didn't have a business degree, getting through the challenges of balancing books--accounts payable, accounts receivable--he had to learn on the fly," he says.

How a career in baseball prepared him for the business world

Piazza came up from the bottom rung: He joined the Los Angeles Dodgers in 1988 as only the No. 1,390 draft pick. Even then, the pick was largely made thanks to his father's relationship to the team's then-manager, Tommy Lasorda. To date, Piazza is the lowest-ever draftee to make it into the Hall of Fame.

The experience taught him a lesson in maintaining perseverance in the face of criticism and failure. "I always tell people that if you don't have confidence in yourself, no one else will," says Piazza. "People can smell when you're not all in."

Self-confidence is especially important when you have a thankless job, says Piazza, who recalls catching for "veteran pitching staff" in his early baseball days. They were often vocal about his shortcomings as a player:

"We [the Dodgers] had Orel Hershiser, Kevin Gross, Tom Candiotti, Ramon Martinez [Pedro Martinez's brother]," he says. "So right off the bat, I was thrown into the fire. I had to elevate my game, and you're talking about a staff that probably had close to 100 years of MLB experience to a rookie. I had to adapt, and these guys did not take it easy on me. After a game, if I made a mistake, they let me know about it, and I had to have really, really thick skin."

His best advice for business owners, drawn from the field: "Don't be sensitive. When someone criticizes you, you have to have the fortitude to take it and process it without getting emotional."

Lessons from watching his father run a company

Piazza was already well-versed in entrepreneurship before his career in baseball. Watching his father, Vince, run a company gave him an inside look at the challenges that many founders face.

The Piazza Auto Group started with just one location in Norristown, Pennsylvania, but expanded over the years to include 12 full-service dealerships across the state. (Piazza's brothers, Tony and Danny, run the dealership now that their father, who is 85, has retired.)

"Small businesses run into these issues that larger businesses have the resources to farm out, so to speak," Piazza says. "My dad had a lot of ups and downs, and there was a lot of competition in the industry." But Piazza was always inspired by his father's willingness to make personal sacrifices for the sake of the company.

"He was insatiable in his work ethic," Piazza says. "He put in long hours. I remember, as a kid, him going to the auto auctions on a Friday night in Manheim, Pennsylvania, to get products and used cars to retail."

In addition to Company.com, Piazza has invested in A.C. Reggiana 1919, an Italian soccer league, and most recently he commissioned Hollywood screenwriter David Franzoni (Gladiator) to pen a television series based on the life of the emperor Constantine.

While Piazza has no definite plans to invest in more tech companies, it's something he's looking into. "I try to keep a radar on for interesting startups. I stick to what I know, and for me, it's more personal. I invest when I get to know people and what they're doing," he says.

Taking a lesson from his father, Piazza believes that when the heart is good, everything else is workable: "Business can be a battleground, but that doesn't mean you can't run an honest business that comes from people."