Dedniel Nuñez was a big weapon for the Mets last summer, but when he returned to the big leagues this year, his ability to throw strikes suddenly disappeared. The 28-year-old, who was a great story as a rookie in 2024 after spending the entirety of his career in the Mets system, was optioned to Triple-A Syracuse on Saturday to make room for left-hander Jose Castillo on the roster.

The Mets sent him back to the minor leagues with instructions to find the strike zone once again after giving up three earned runs over 3 2/3 innings. He faced 18 batters and walked six of them.

“Even though the past two outings he’s been better, we just need to see consistency with the strike zone,” manager Carlos Mendoza said Saturday at Yankee Stadium. “That’s what made this guy elite last year and became who he was last year. For us, the first couple of outings, we saw the inconsistencies with the strikes, but it was good to see him yesterday hit 98 and he was a lot better. So he’s just got to go out down there and continue to find that consistency and just continue to throw strikes.”

Nuñez walked the bases loaded in his first outing without getting an out and Reed Garrett couldn’t hold the inherited runners on base. In his second outing, he walked two and struck out two, again leaving a jam for Garrett. He then settled into his next two outings, throwing clean innings against the Pittsburgh Pirates last week, and gave up a hit and walked one against the Yankees on Friday night.

Still, it became a numbers game with the Mets needing to find a spot for Castillo, who was acquired in a trade with the Arizona Diamondbacks for cash considerations on Thursday night. A 6-6 hard-throwing Venezuelan, Castillo was once a highly-regarded prospect for the San Diego Padres after being traded by the Tampa Bay Rays. He’s been sidelined by injuries in recent years, undergoing Tommy John surgery in 2021.

The Mets see a pitcher with potential. The addition of Castillo now gives them two left-handers to replace A.J. Minter and Danny Young, both of whom required season-ending surgeries.

“We feel like there’s more in the tank there,” Mendoza said. “Hopefully he can be a player for us out of the bullpen.”

Castillo, 29, has a 5.21 ERA over 46 2/3 Major League innings.

Infielder Ronny Mauricio completed his rehab assignment and was optioned to Triple-A Syracuse. A power-hitting prospect, the Mets want him to get used to playing every day after being out of baseball for more than a year with two knee surgeries.

“He needs to become a normal baseball player, getting used to playing every day without restrictions,” Mendoza said. “[Instead of saying], ‘Hey, you’re only playing five innings, or you’re only playing seven,’ he needs to continue playing full games, continue to play [on] back-to-back days, 3-4 games in a row. He’s not there yet, so we’ve got to get him there. I think it’s just more getting everyday at-bats, everyday reps and then we’ll go from there.”

Right-hander Paul Blackburn will make one more rehab start, throwing around 75 pitches.