MILWAUKEE -- Saturday was a "good news, bad news" kind of day for the Blue Jays, who lost 5-4 to the Brewers at American Family Field.

On one hand, left-hander Yusei Kikuchi struggled yet again, allowing in five runs (two earned) including a pair of homers while lasting just two innings. But on the other side, Toronto may have found a potential replacement should they need to fill a spot in the rotation in the future.

That is none other than Max Castillo, who dazzled in the second outing of his big league career with four scoreless innings of relief. The young right-hander allowed just one hit -- a single to Christian Yelich with two outs in the eighth -- and struck out seven while walking two.

"He was outstanding," Blue Jays manager Charlie Montoyo said. "He did a great job to try and keep us in the game."

Nearly four years removed from his last appearance on MLB Pipeline's list of the club's Top 30 prospects, Castillo started the 2022 season with Double-A New Hampshire, where he posted a 3.10 ERA over six starts. That was enough to earn a callup to Triple-A Buffalo, where his 0.66 ERA over 27 1/3 innings earned him his first big league promotion earlier this month.

After allowing a pair of home runs to the Yankees in his debut on June 19, Castillo admitted to being a little nervous. It was a much different story Saturday, which he attributed to the help of his fellow bullpen mates.

"When you're coming from the Minor Leagues to the big leagues, you get very emotional and a little nervous," Castillo said with the help of team interpreter Hector Lebron. "Thankfully, I'm past that. The guys in the bullpen have helped me out and given me advice, and I appreciate it."

For now, Castillo expects to remain in his long relief role. And at the moment, at least, Montoyo doesn't have plans to change Kikuchi's role, either. But with a 10.13 ERA over his last four starts, a change might be necessary down the road.

"We'll see," Montoyo said. "His stuff is there. It's not like he's throwing 90-91, this guy throws 97. It's all about throwing strikes. When he throws strikes, he gets people out. We all know he has good stuff but at the end of the day, you have to throw strikes."

Kikuchi struggled with that Saturday, at least early on in counts. That forced him to come back into the zone to try and catch up, and the results spoke for themselves.

"The pitches when I'm trying to get back into the count are the ones that are getting hit hard," Kikuchi said. "It was the same thing today, unfortunately."

Physically, Kikuchi feels fine. Montoyo said before the game that he'd been working hard in between starts hoping to iron out any issues with his delivery and Kikuchi expects to do the same over the next few days.

But even if it's not quite time for a switch just yet, Castillo's name will certainly be in the discussion if that time does come.

"People have to show you they can pitch at this level," Montoyo said. "That's what he did today."