Lucas Giolito, Max Fried and Jack Flaherty were teammates nine years ago at Harvard-Westlake, a prestigious prep school in Los Angeles.

On Thursday, all three will be opening-day starting pitchers in the major leagues.

And they didn’t even win a California state title the year they all played together.

“If you point at a particular high school and ask: What is the probability that three baseball players graduating this year will wind up pitching for MLB teams, and get selected to be this year’s starters on opening day? The probability is less than one in a billion,” said James E. Corter, professor of statistics and education at Columbia University’s Teachers College.

“But if you assume that there are maybe 10,000 high schools in the U.S., and elsewhere in the hemisphere that field baseball teams who play at a level that might get them noticed and recruited, the odds that it could happen somewhere, with some high school, rise considerably,” Corter said. “So now we’re talking more like one in 100,000. Still, pretty unusual.”

Giolito becomes the first White Sox right-hander to make consecutive opening-day starts since Jaime Navarro in 1997 and ’98 when Chicago opens under new manager Tony La Russa at the Los Angeles Angels, and Flaherty will start his second opener in a row when the St. Louis Cardinals are at the Cincinnati Reds. Fried takes the mound in an opener for the first time when Atlanta plays at Philadelphia.

“It’s pretty cool when you know 10% of the league is starting opening day from the same high school,” Giolito said. “We’ve been working together for a long time, pumping each other up. It’s pretty weird and wild. I don’t think that’s ever happened before in any professional sport where you’ve got three guys from the same high school all competing on the big stage.”

Flaherty was 6-1 with a 1.77 ERA and a save as a sophomore for the Wolverines and Fried was 8-2 with a 2.02 ERA as a senior. Giolito got hurt early his senior season and finished 2-1 with a 0.84 ERA.

Harvard-Westlake’s baseball team went 24-5-1 in 2012 and lost to Valencia 3-1 in the second round of the playoffs. One year later, Flaherty pitched a six-hitter and had an RBI single to beat Marino 1-0 in the 2013 California Interscholastic Federation championship game at Dodger Stadium.

“The most fun was getting to go to bed the night before and knowing that I had somebody really good going to the mound the next day. There wasn’t a whole lot of sleepless nights during that that period of our program’s history,” said Matt LaCour, Harvard-Westlake’s baseball coach from 2002-15 and now one of its athletic directors. “It was pretty easy to tell by the time they got into their junior, senior years that they were all going to be the type of high-profile, highly sought-after draft picks that they became. I guess with Jack it was a little bit different than the other two. We weren’t quite sure if he was going to be an offensive player or a defensive player when it came to pro baseball.”

Fried first attended Montclair Prep in Van Nuys, then transferred after his school eliminated baseball and other extracurricular activities. Flaherty was entering his sophomore year in 2011-12, considering himself a shortstop, and Giolito was starting his senior season. By 2012, Giolito had reached 100 mph in a winter league game and was projected as a possible No. 1 pick before spraining the ulnar collateral ligament in his pitching elbow, which led to Tommy John surgery that Sept. 13.

“I knew they were going to be successful based on the talent, the work ethic. Did I think that all three of them would be starting opening day? No, I couldn’t imagine that,” said pitching coach Ethan Katz, then with Harvard-Westlake and now starting his first season with the White Sox.

Flaherty viewed the others as potential opening-day starters but not himself — because he didn’t foresee his future on the mound.

“We definitely knew that Lucas and Max were going to start on opening day together at some point, and I think I was the third one that was kind of added to that,” he said. “Those guys have been studs in the last couple of years. It’s fun to be surrounded by guys of that caliber and have relationships with them.”

Confidence was not lacking: the trio viewed themselves as future big leaguers. Giolito will check out the starts of the other two and perhaps “compare and contrast.”

“That was the kind of stuff,” Giolito recalled, “we were talking about back when you were 15, 16, 17 years old: We’re going to be in the big leagues. We’re going to be starting games. I don’t know if we ever had a specific conversation about all starting on opening day. We were probably talking a lot about wouldn’t it be so cool if we were on the same team? But it’s definitely a very weird thing and a very awesome thing to be a part of that. I don’t know if that will ever happen again in pro sports, something like that. Hopefully we’re all starting opening days for the rest of our careers.”

And, indeed, all three became first-round draft picks. Fried was selected seventh by San Diego in 2012 and Giolito 16th, while Flaherty was taken 34th by St. Louis in 2014.

And all three were bonus babies, with Fried signing for $3 million, Giolito $2,925,000 and Flaherty $2 million

Giolito, a 26-year-old right-hander, became an All-Star in 2019. He was 4-3 with a 3.48 ERA last year and is 31-29 in four seasons.

Fried, a 27-year-old lefty, went 7-0 with a 2.25 ERA last year, improving to 26-11 in four seasons. He won a Gold Glove and finished fifth in NL Cy Young Award voting.

“It’s been in Ohio as early as the mid-1850s at least, brought in as an ornamental plant because of its unique foliage and white flowers,” Gardner said. “It was actually planted in people’s landscaping, and it has been spreading.”

Flaherty, a 25-year-old right-hander, was 4-3 with a 4.91 ERA, leaving his record at 23-22 in four years.

During offseasons, Fried and Flaherty still work out at Harvard-Westlake.

“I’m really happy and really excited for those guys,” Fried said. “They’ve worked extremely hard to be able to put themselves in that position. To kind of share that and be able to be pitching at the same day as those guys is pretty cool.”