Unlike his first big league stint, which lasted a mere three days, the Marlins intend to have first-base prospect Lewin Diaz stick around awhile.

Manager Don Mattingly added on Tuesday before the Marlins faced the Mets in Game 1 of a doubleheader at Citi Field that Díaz also is expected to play regularly.

Díaz is the latest Miami prospect to be given an opportunity to launch his big league career.

“We didn’t have to bring up Lewin at this point,” Mattingly said. “This is one of those that we wanted to bring up Lewin. We felt like it was the right time. He’s going to get quite a few at-bats, and get a lot of chances.”

Ranked by MLB Pipeline as Miami’s No. 8 prospect, Díaz is a left-handed-hitting complement to right-handed-hitting Jesús Aguilar.

The two will likely alternate between first base and designated hitter.

“He’s got a lot of talent,” Aguilar said of the rookie. “I’ve got no doubt that he can do the job. That’s why he’s here. He’s going to do things the right way. I think he’s a superstar. He can hit. He can play defense.”

The Marlins are able to make this situation work because of the availability of the designated hitter.

“I think we’re going to be all right, with that mix between me and him,” Aguilar said. “I know he can do the job, too.”

Díaz was originally called up on Aug. 15 when left fielder Corey Dickerson was placed on MLB’s bereavement list. The rookie went 2-for-8 in two starts and a pinch-hit appearance.

Once Dickerson returned, Díaz was optioned back to the alternate training site in Jupiter, Fla.

The way he looked in that short stay reinforced the Marlins' conviction that the rookie can handle playing regularly. Díaz also stood out in Spring Training, so there wasn’t much convincing the left-handed hitter needed to do to win over the coaches and front office.

Experienced players like Jonathan Villar and Aguilar also helped embrace Díaz since Spring Training. The veterans eased the pressure for Díaz during his first opportunity.

“They made me look good,” Díaz said through an interpreter about his first big league opportunity. “I had good at-bats. I think that got me brought back here.”

Patience vs. performance
How to fully assess Lewis Brinson remains a difficult call for the Marlins, who are showing patience with the 26-year-old outfielder while also seeking performance.

Used sparingly right now, Brinson finds himself in the lineup mostly against left-handed starters. Overall, he’s off to a slow start. Entering Tuesday’s doubleheader, he was batting .107 (3-for-28).

Even with the struggles, Brinson shows flashes of why he was once a Top 100 prospect. Playing center field on Sunday at Washington, Brinson made one of the highlight catches of the entire MLB season, leaping to rob Juan Soto of a two-run homer.

Brinson covered 99 feet in 6.4 seconds to make the play, according to Statcast.

“This is a tough one because he looked so good in the spring,” Mattingly said. “It looked like he made some changes. I still think he looks like that. I still think he looks good. It’s better than before, for me. We’re in a situation where he’s not playing every day. I still think there is a lot in there with Brins. That’s the one thing I will say.”

At the plate, there are inconsistencies in making contact. When he does get into a pitch, he’s among the strongest players on the team.

The Marlins have had three balls in play tracked by Statcast at 110 mph or higher. The hardest was Monte Harrison, 112.6 mph, on Aug. 17 against the Mets. The second is Brinson, 112.2 mph, on Aug. 15 against the Braves. Villar has the other, 110.6 mph, on Friday at the Nationals.

All three were doubles.

“You’re just not willing to give up on Brinson, from the standpoint, this is a crazy year," Mattingly said.

Brinson was the headliner in the Christian Yelich trade with the Brewers after the 2017 season. Brinson has one option left, meaning that he could be sent back to the alternate training site, if the organization decides to go that way.

“In my mind, and I think in the organization’s mind, we exhaust every opportunity with Lewis, because we see the ability, and know it’s in there,” Mattingly said. “So it’s just trying to get to it. We’re trying to be patient, and let it keep coming.”

Roster moves
Lefty reliever Josh D. Smith was appointed as the Marlins’ 29th man for Tuesday's doubleheader, and catcher Ryan Lavarnway cleared waivers and was outrighted to the alternate training site.