MIAMI – For Isan Diaz, it’s a matter of when he will be promoted to the big leagues this season.

Ranked by MLB Pipeline as the Marlins’ No. 6 prospect, Diaz continues to make strides at Triple-A New Orleans. The left-handed-hitting second baseman has 22 home runs and 61 RBIs.

Diaz participated in the Sirius XM All-Star Futures Game and made a couple of impressive plays at second base. Since, he has raised his slash line to .306/.398/.581, with 18 doubles and two triples.

“Isan has been really good,” Marlins manager Don Mattingly said. “Our development [staff] is doing a great job with him.”

Now, it’s a matter of how much more seasoning the Marlins want from Diaz, who is pretty much big league ready. The only thing he hasn’t shown in recent years is sustained consistency.

In 2018, his first season in the Marlins’ organization, Diaz hit .245 in 83 games at Double-A Jacksonville, and .204 in 36 games at Triple-A New Orleans.

Diaz got off to a slow start this season, batting .226 in April. He picked things up in May, June and thus far in July.

“We had seen a lot more inconsistency with him last year,” Mattingly said. “He’d get his hits for a few days and then a number of days when he’s not really getting his hits. Now, it seems like he’s getting his hits almost on a daily basis.”

Defensively, Diaz has made great strides and is playing plus defensively at second base. He has played third base in Winter Ball and has the arm strength to handle second or third. But, for now, the organization appears reluctant to use Diaz at third base.

Starlin Castro is Miami’s everyday second baseman. The club is listening on potential trade offers for Castro.

Castro’s status aside, the Marlins, in a season where they are building, are not rushing Diaz’s development. They also would like to see him show consistency for more than just a few months before pushing him to the big leagues.

“The reports you read, his at-bats are good,” Mattingly said. “Isan is in a good spot in where he’s at in his development.”

Worth noting

• Lewis Brinson, the Marlins’ center fielder for the first month, continues to work on his development at New Orleans. In 67 games, he’s hitting .266 with 13 home runs and 47 RBIs. But he’s been in a slump lately, batting .146 in his last 10 games.

“Brinson, early on, was really good,” Mattingly said. “He’s had a stretch here lately where he’s been on a little swoon. But, overall, they like the swings he’s taking.”

• Infielder Martín Prado (right hamstring strain) was brought back from his Double-A Jacksonville rehab assignment, and he took batting practice with the Marlins on Wednesday.

“He’s going to work out with us today, and we still haven’t made a decision on what’s next,” Mattingly said.