GLENDALE, Ariz. — Wherever Jesse Hahn goes, the same inspiration follows.

At Fitch High School in Connecticut, while playing on the same team with Mets pitcher Matt Harvey; at Virginia Tech; in the Tampa Bay organization; with the Padres; and now with the A’s, Hahn has looked to his sister, Melissa, to brighten his day.

Melissa Hahn, 34, has cerebral palsy, and she’s back home in Groton, Conn., in a wheelchair, but she watches any time her brother is on TV.

“She’s my No. 1 fan. She’s always in front of the computer or the TV for my games,” Hahn said. “She has this cute little Spongebob or Barbie phone she puts on her tray and she always expects me to call her after every start, or I call my dad and he puts her on the phone and I talk to her.”

“She just lights up when Jesse is around,” said Hahn’s friend and former pitching coach, Mike Evans. “It’s nonstop smiling. Both of them just love each other. It’s a great relationship.”

Hahn, who looks like a lock to be in Oakland’s rotation to start the season, has a tight family bond, period. He calls his parents, Fred and Kate, the biggest and best influence on him, and Fred Hahn shaped his son’s baseball career from the very start.

“He was everything,” Jesse Hahn said. “He spent a lot of time with me down at the park. I was the pitcher, he was the catcher. So while the other kids were in the house playing video games, we were in the park every single day throwing, and whatever we found that worked well, whatever grip — like for me, my curveball — anything that looked good, he’d say to stick with it.”

Evans used to be in the park with his younger brother, Tommy, and they’d see the Hahns there every day — that’s how they met. “They’d go and throw and throw and throw, and we’re doing the same exact thing,” Evans said with a laugh. “Jesse is so nice. He’s the most likable kid in our town, and his dad is the same way. I could talk to them for days.”

Evans wound up coaching Hahn on an American Legion team, and his brother, Hahn and Harvey all pitched at Fitch in one of the all-time great high-school rotations. As a senior, Hahn struck out 65 batters in 40 innings and set a state record with an 0.17 ERA.

“We kind of fed off each other,” Hahn said. “If Matt pitched well, it motivated me to pitch well. He attracted scouts and colleges, so did I. We always wanted to be in that same category as each other and play in major-league baseball together. It’s pretty unique.

“He was almost the same pitcher in high school: He threw hard, blew through hitters. We knew it was only a matter of time before he was going to take off.”

For Hahn, things came a bit slower. First, he had to gain some weight. A stringbean as a senior, he was throwing 90 mph. His first year at Virginia Tech, he added 30 pounds, and by his sophomore year, he was throwing 100 mph.

In his junior year, Hahn needed Tommy John surgery, but even so, Tampa Bay selected him in the sixth round of the draft in 2010, knowing Hahn couldn’t pitch until 2012. Before the 2014 season, he went to San Diego in a seven-player deal, and the 6-foot-5 right-hander made his big-league debut with the Padres, jumping from Double-A and going 7-4 with a 3.07 ERA in 14 games.

“Good arm, good feel to pitch, good curveball,” San Diego manager Bud Black said, rattling off Hahn’s attributes. “What do I like? His pulse. I like the heartbeat, man. He competes. He’s calm. He’s also a really good basketball player.”

Padres general manager A.J. Preller, who took over the team in August, didn’t get a chance to know Hahn very well before trading him to the A’s in the Derek Norris deal, but Preller checked around the organization.

“Just hearing about the comments from everyone around here — usually, it’s 50-50 when you ask people’s opinions, and with Jesse, it was 100 percent. Everyone was way on board with him, his makeup, his competitiveness, so it was tough to move him,” Preller said. “We kept hoping the A’s would come back with a different name, but (they) didn’t.”

Said Hahn: “It was definitely bittersweet. San Diego gave me every opportunity to prove myself. At the same time, it was really cool that Billy Beane wanted me on his team. I was very excited to get over here and continue my journey.

“I was a fan of 'Moneyball’ the movie and the system they run here. They give everyone a chance. There’s a lot of young pitching that will get a chance throughout the year.”

Going by the current rotation, Hahn could well be pitching in the second spot, behind Sonny Gray. And although he’s certainly not counting on anything, he hopes to be with the team and on the mound in early June in Boston or July in New York — so his family, which also includes younger sister Stephanie, can see him pitch. Especially Melissa.

“She saw me in college, but it’s hard for her to travel,” Hahn said. “She’s the toughest girl I’ve ever met. She’s been through a lot but she’s happy. She’s a fighter. I get all my motivation and fight from her.”

Susan Slusser is a San Francisco Chronicle staff writer. E-mail: sslusser@sfchronicle.com Twitter: @susanslusser