Like his love for the game, he got it from Dad.
"When we took batting practice, it was never, 'Let's hit line drives,'" Cust said with a laugh. "It was, 'Let's hit balls over the lights!'"
Yet if there was even a twinge of sadness in the heart of Jack Cust Jr. as he watched his son, Jack Cust III, spray line drives all over the field early in batting practice before a recent game against the New York Yankees, he hid it quite well.
"It's a dream come true," the father said. "For both of us."
It's a dream on which the son nearly gave up. He didn't because of his dad.
Many A's fans know all about Cust's rags-to-riches story. In fact, many fans around the country know it, too, thanks to his breakout 2007 season.
The Cliff's Notes: Huge high-school star in New Jersey; state player of the year; first-round Draft pick; never quite catches on with anyone; hits 200 homers in the Minors; finally gets a shot with Oakland; hits eight homers in first week; goes on to lead team in homers and RBIs.
What a lot of fans probably don't know is that one of the teams with which Cust was unable to catch on was Oakland, and that nearly proved the proverbial back-breaking straw.
The A's had long coveted Cust, whose knowledge of -- and discipline within -- the strike zone often gets overlooked in the vapor trail of his huge hack, when they acquired him before the 2005 season. But Cust, whom Jack Jr. knew was the kind of patience-and-power prototype that would get a long look from the A's, was slowed by a wrist injury and never made it up to Oakland.
"I thought maybe that was my last opportunity," said Cust, who batted .257 with a .402 on-base percentage, 19 homers and 75 RBIs in 2005 for Triple-A Sacramento.
When Cust moved on to the Padres organization the next season and again put up big power numbers, his dad started talking about the A's again.
"He said, 'You need to get back to Oakland; they value what you do there,'" said Jack III. "I said, 'Oakland's not the right fit. They had me and didn't want me. It didn't work out.'"
Eventually Dad, who snapped his son out a bit of a mental funk during their offseason time together at a baseball school they founded together, was proven prophetic.
The A's came calling again when Mike Piazza went down with a shoulder injury last May.
And now Jack Jr. is watching his son spraying line drives.
"It still bugs him," Jack III said, laughing again. "After I turned pro, in the winter we'd go hitting and he'd say, 'I don't have time for this getting-loose-on-the field stuff. Let's hit!'"
So the son hits. The father smiles.
"He gets all giddy about it," Jack III said. "He's just as happy as I am. He put a lot of work into this, too."
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.