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TORONTO -- Snapchat memories from a year ago are popping up on James McArthur’s phone, and there’s one in particular that sparked a realization from him and his wife, Kate, about how much things have changed since last May.

McArthur is standing in his apartment in Lehigh Valley, Penn., with his daughter in his arms, holding up one finger to signal his first day in the Royals’ organization. Soon after that picture came photos of McArthur dressed in Royals blue, a stark contrast from the Phillies red he’d known since he was drafted in 2018.

The difference between the two colors only serves as a reminder of the difference in McArthur. In less than a year, he’s gone from a starter designated for assignment to the closer on a winning Royals team, with seven saves and a 2.63 ERA.

“It’s really crazy,” McArthur said. “Thinking about where I was a year ago as a pitcher to where I am now, there’s just been so much growth and development. I’m really grateful.”

On May 8, 2023, the Royals acquired McArthur for Minor League outfielder Junior Marin and cash. It was a minor trade at the time; McArthur was a fringe-roster player, and the Phillies needed bullpen help and a 40-man spot for Jeff Hoffman in late May.

The Royals were taking a flier on McArthur, then a 26-year-old starter. The Phillies had protected the 6-foot-6 righty from the Rule 5 Draft in 2021, but McArthur got hurt in '22 and logged just 16 innings above Triple-A in '23.

The trade has become anything but minor. McArthur has not only thrived in the Royals’ bullpen, but also become the prime example for many of the changes Kansas City has made over the past two years.

When McArthur was DFA’d, the Royals’ Major League pitching team took note of his pitch profiles, delivery and past performance and saw potential. The group immediately raised its interest to the front office and pushed to acquire him.

“There’s a reason he’s on the waiver wire, but is there something we can do to help?” pitching coach Brian Sweeney said. “We saw some reliever mentality. Seeing his breaking ball, we thought it was a good one. But we thought he was missing a slider. And we said, ‘We can help this guy.’”

It was the first year general manager J.J. Picollo had more voices weighing in on these types of decisions, and the scouting and data reports matched up with what the coaches were saying. For four days until the trade was made, all he heard was excitement from the staff to bring McArthur into the organization.

“It was a good opportunity to see where it would go,” Picollo said. “We weren’t playing well at the time. Honestly, [I thought], 'Let’s see if they can make some changes that will be helpful down the road.' … They had a definitive plan in mind: 'If we get him, this is what we’re going to do.'

“I could hear the conviction in their voices, and it made me feel like, ‘We need to make this deal.’”

In his first two weeks joining Triple-A Omaha, McArthur had Zoom calls with Royals coaches that included Sweeney, assistant pitching coach Zach Bove, bullpen coach Mitch Stetter, senior pitching director Paul Gibson and Triple-A pitching coach Dane Johnson.

The biggest change they wanted McArthur to make was adding a slider. They knew how well he could spin the ball from his curveball and believed a second breaking ball could help him cover more of the zone.

He was all for it.

“I was searching for an answer in some ways, so for me, it was a no-brainer,” McArthur said. “It was like, ‘All right. This is a new organization, and if they think it’s going to help me, I’ll give it a go.’”

Getting comfortable with his slider was his sole focus in Triple-A, working daily with Johnson on finding the best grip for the pitch. Then, he worked on the pitch specifically to lefties.

McArthur was called up on Sept. 2 last year, and he stayed with Kansas City for the remainder of the season, firing off 16 1/3 scoreless innings while earning his first save on Sept. 18 and two more before the season ended.

McArthur ended the year with a 30% whiff rate on his new slider, and the addition of it made his curveball better. Hitters had just a .194 average on McArthur’s hammer with a 35.3% whiff percentage. His velocity jumped on his sinker, which continues to see more movement this year, too.

The Royals retooled their pitching staff this offseason and brought veteran relievers in to steady the bullpen and throw high-leverage innings, but McArthur’s potential in the back-end of games always factored into their plans.

Two weeks into the season, he took over ninth-inning duties when Will Smith struggled.

And McArthur is still trying to improve. As important as the slider has been for him, throwing his sinker to both sides of the plate has been just as helpful. He’s tinkering with a four-seamer and a cutter, which he’s thrown before, too.

“The weapons are getting there,” McArthur said.

For the small-market Royals to be competitive, drafting well and producing homegrown players is paramount. But they need to continue to find players like McArthur, those who can benefit from a change of scenery and the ideas that Sweeney, Bove, Stetter and others bring daily.

“The process to acquire him was great, with a lot of input from different people … and the collaboration to see what they thought he could become,” manager Matt Quatraro said. “And then once we acquired him, the tweaks to the usage and pitch design, that part of it is really exciting because that shows a lot of work within departments and finding a diamond in the rough. A lot of credit to him, too.”

Before McArthur could get truly comfortable with the new pitch, the Royals needed a fresh arm in the 'pen at the end of June. McArthur made his MLB debut on June 28 and gave up seven runs to the Guardians, who crushed his sinker. He threw two sliders, both balls.

“I just felt so bad for him,” Stetter said. “Went up to him at his locker and was like, ‘Keep your head up, next one’s going to be better.’ He got sent out right away, and we gave him a plan: Get the slider going.”