SEATTLE — All Royals outfielder Jorge Bonifacio wanted was a boost.

Some seven months ago, fresh off his first season in the major leagues, Bonifacio returned home to play winter baseball in the Dominican Republic. He wanted to continue his development, encouraged by his future with the Royals.

But he was tired, body sore from playing 113 major-league games. He needed something to get him through at least a month of additional playing time. He sought the boost from the B12 vitamin without running the supplement by the Royals training staff.

This was the decision that cost him an 80-game suspension, Bonifacio told The Star at Safeco Field on Friday, one day after being reinstated from the restricted list.

“I never expected that result,” Bonifacio said in Spanish.

Upon reporting to spring training in Surprise, Ariz., in February, Bonifacio found out the B12 he purchased in the offseason had been laced with Boldenone, a performance-enhancing substance commonly used to treat horses that is prohibited by the World Anti-Doping Agency and banned by baseball.

Bonifacio immediately owned his mistake and issued a public apology to his teammates and the Royals organization after he was suspended on March 10. General manager Dayton Moore commended Bonifacio taking responsibility for his actions but was still puzzled.

“He knows better. Shouldn’t have done it,” Moore said when asked by The Star about the suspension in April. “These guys were told don’t put anything in their system other than water without speaking with Nick Kenney. They’ve been educated. He just made a mistake.

“But he’s an incredible person. He’ll learn from it and he’ll be better for it.”

At the time, Bonifacio was disappointed he couldn’t continue to build on a rookie campaign that saw him bat .255 with 17 home runs. He instead found himself banished to the desert, clinging to a cellphone as a lifeline to a team that stumbled to a 25-55 record without him.

He exchanged messages of encouragement with his older brother, Emilio, the one-time Royals player who went unsigned as a free agent this winter. Royals catcher Salvador Perez frequented his inbox, too.

“I was talking to Salvy a lot, saying, ‘Let’s go, let’s go, you guys can do it. Just try to get everyday better and better,’ ” Bonifacio said. “The team wasn’t playing very well and he told me, ‘Hey, bro, we need you here.’ And that was more tough for me because I couldn’t do anything down there.”

The mutual encouragement was necessary for Bonifacio, 25, to remain focused on the present. Otherwise, thoughts of his misguided judgment might have crowded too much of his mind.

He still doesn’t have an answer for how the supplement he obtained came to be tainted. Yet it doesn’t matter, he acknowledged.

“It was just by accident,” Bonifacio said.

Bonifacio spent the last three and a half months tucked out of public view, ruminating on his mistake and preparing himself for a shortened season. He played four or five times a week in extended spring-training games, facing what he referred to as “wild” pitchers to stay sharp.

He kept his focus on June 29, the day of the first major-league game he would be eligible to play.

The date finally arrived with the Royals in Seattle to face the Mariners, who are in second place in the American League West division. The team Bonifacio rejoined is in polar-opposite shape: The Royals on Saturday morning found themselves 31 games under .500, stuck in the cellar with the second-worst record in baseball.

“We’re glad to have him back,” manager Ned Yost said. “The kid hit 17 homers last year. He was gonna be in the middle of the order until all this surfaced.”

Of course, it will take more than Bonifacio’s return to slow down the Royals’ pace to 110 losses. But his presence in the lineup is a step in the right direction.

“I just have to leave it behind,” he said. “I can’t turn back the clock. I just won’t do something like that again.”