Orioles left fielder Hyun Soo Kim runs down this flyball in early July. Back in the spring, in his first season over from the Korean Baseball Organization, he was pressing at the plate and not endearing himself to Baltimore fans. (Patrick Semansky/Associated Press)

The mixed reception Hyun Soo Kim received on Opening Day needed no translation. Amid some cheers, a reverberation of boos transcended language and culture. After the Baltimore Orioles outfielder refused an assignment to the minor leagues out of spring training, a right stipulated in his contract, some critics let Kim know how they felt.

Outfielder Adam Jones noticed something when Kim would turn around to look at the fans who were yelling at him. “If someone is saying something to him, he just looks at them like, ‘I don’t know what you’re saying,’ ” Jones said.

But as Kim stepped up to the plate in a recent game against the Los Angeles Angels, batting second, he received a warm reception, making the Opening Day boos seem like a distant memory.

It certainly helps that Kim is performing at a high level since earning a significant role in the Orioles offense, batting .329 with a .410 on-base percentage.

But to understand why Kim, prior to going on the disabled list Tuesday with a strained hamstring, looks like a different player than the one who couldn’t buy a hit in March, one needs to understand the world-flipping transition that an international player goes through.

From left to right, Baltimore Orioles outfielders Hyun Soo Kim, Adam Jones and Joey Rickard bow after a game against the Los Angeles Angels on July 9. (Patrick Semansky/Associated Press)

“[Kim] was an easy target,” Jones said. “[The critics and angry fans] were insensitive bastards.”

Spring training, for many in Major League Baseball, is viewed as the calm to get players ready for the marathon that awaits. That time is used differently in the Korean Baseball Organization, where Kim had played since 2007.

For teams in the KBO, spring training starts overseas, mostly in Arizona, nearly a month before teams in MLB. By the time Opening Day comes around during the first few days of April, KBO teams have been playing for three months.

For Kim, spring training with the Orioles presented the challenges of needing to work on an accelerated schedule, adjust to a foreign culture and language and meet expectations domestically and internationally.

For any immigrant coming to a new country, assimilating is overwhelming enough.

“I knew that I needed to adjust quickly, so I put all of my focus and energy into that,” Kim told The Post in Korean. “I thought that culturally, I needed to come here and figure things out for myself because I didn’t have any idea what to expect.”

Different backgrounds

The transition for Asian players differs from that for those from Hispanic countries.

Orioles fans have warmed up to the player they were skeptical about coming out of spring training. (Mitchell Layton/Getty Images)

Many teams, especially in the Dominican Republic and Venezuela, have the infrastructure and academies in place to help young players adjust to being a professional athlete in the United States.

And with more than 25 percent of baseball players identifying as Latino, the language block isn’t as great as it is for Asian ballplayers. There are 21 Asian-born players in MLB, including eight from South Korea.

“[Kim] can’t read the signs, can’t understand when we’d sit there speaking in English and Spanish through the clubhouse,” Jones said. “He’s the only one who speaks his own language. He’s sitting there in his own world.”

Back in Korea, all eyes were on Kim. According to Jeeho Yoo, who covers baseball for Yonhap News, the South Korean news agency, Kim’s move to the United States contributed to the opening of a new sports cable station in the country that broadcasts MLB games featuring Korean baseball players.

“We get pretty saturated coverage of [those games],” Yoo said. “Virtually every game involving a Korean player is on cable. Newspapers, news wires and online outlets write about the players’ heroics extensively.”

Kim’s performance in spring training added more fuel to the fire, as he hit just .178 in 45 at-bats. And with outfielder Joey Rickard coming out of camp hot, hitting .397 with six doubles, the clamor for Kim to go to the minors grew louder.

Despite coming into spring training as a presumptive starter — Kim batted .326 with 28 home runs and 121 RBI in the KBD last season and owns a .318 career average in the league over 10 seasons — the question was no longer was whether he deserved to be in the Opening Day lineup. It was whether he deserved to be in the majors at all.

There was a bad precedent: Suk-min Yoon’s failure to make the majors after signing with the Orioles in 2014 was a setback for Korean success in Baltimore.

So when Ken Rosenthal of Fox Sports mentioned Yoon, who returned to Korea after one season, while reporting on Kim’s situation, it brought up the possibility of whether the team should let its new outfielder return to Korea if he did not want to go to the minors.

Neither possibility occurred to Kim.

“Not once did I think about returning to Korea,” Kim said.

But Kim gets a little more anxious when asked about why he was unequivocal about staying in the major leagues.

“Rather than say I have a lot of confidence about my abilities as a baseball player, I had to do more of the things that I could control,” Kim said. “There’s really a lot of things I could say, but I’ll stop there.”

Orioles General Manager Dan Duquette expressed his desire to not have Kim on the Opening Day roster. And while Duquette had yet to discuss the decision with Kim, the public proclamation seemed to make the move final.

“In these cases, the transition takes some time,” Duquette told the media at the time. “I believe he wants to give it some more time.”

Kim, on the other hand, ignored the speculation.

“It’s not like I wasn’t interested, but I pretend like I don’t hear it, don’t see it. I put effort into that,” Kim said. “I’m really good at being patient. I just wanted to wait until the noise passed. I was going to figure things out.”

Figuring things out

The sample size for Kim’s success in the majors, 152 at-bats, isn’t substantially greater than the amount of time that led some to conclude that the 28-year-old didn’t have a future in the majors.

But what’s different is that there’s very tangible evidence of progress on the field.

“He was pressing a little bit in spring and I didn’t see that selectiveness,” said Orioles Manager Buck Showalter. “He wasn’t going to get anybody’s attention with two walks.”

The Orioles have welcomed Kim into the clubhouse. Many have gone out to eat Korean barbecue with him and tried the many Asian snacks that are brought into the clubhouse. When Showalter organized a “bibimbap” meal, a traditional Korean dish, for Kim in spring training, Jones presented the food with a 90-degree bow, a formal Korean custom.

Kim said he has had no issues adjusting to the major league clubhouse. Rickard said that any time a member of the team hits a home run, Kim is always the first guy to start throwing sunflower seeds in celebration.

And while it’s no guarantee that Kim is going to continue his success at his current clip, Showalter said the success is a reminder not to jump so quickly on a player for early struggles. As Byung Ho Park, who many expected to be a staple in the Minnesota Twins’ lineup, sits in the minors, Kim continues to succeed in the majors, despite being the player many expected to see in Class AAA.

“I never thought I didn’t belong,” Kim said.