Marlins’ Jazz Chisholm Jr. expected to miss extended time with back injury. The details

Daniel A. Varela/dvarela@miamiherald.com

A CT scan on Miami Marlins All-Star second baseman Jazz Chisholm, Jr.’s back has revealed a stress fracture, sources told the Miami Herald on Friday.

Chisholm is expected to miss about six weeks with the injury, which points to early September as the likely earliest return.

Chisholm, who was named the National League’s starter at his position after winning the fan vote, has been on the injured list since June 29 with a right lower back strain and has been rehabbing at the Marlins’ spring training complex in Jupiter. He did not play in the All-Star Game but did make the trip to Los Angeles to take part in the festivities surrounding the game.

Chisholm took batting practice on the workout day Monday at Dodger Stadium even though he was not going to play. He did not take batting practice on the day of the game Tuesday.

Prior to the All-Star Break, Marlins manager Don Mattingly said Chisholm had been feeling fine when it came to swinging, taking groundballs and throwing but was having trouble running.

About a week later, the problems continued to persist.

“You feel bad,” Mattingly said pregame Friday before the Marlins opened a three-game series with the Pittsburgh Pirates at PNC Park. “He’s having a really good year, obviously made the All-Star team. You got a feeling something was wrong when he wasn’t able to get to that All-Star Game and be able to play because we knew it was something that he would have pushed himself to get to be able to play.”

So what’s next for Chisholm over this (at minimum) next month and a half?

“We just take the steps forward to get him right,” Mattingly said, “and let that process take shape and go with it wherever it goes.”

His extended absence doesn’t bode well for the Marlins, considering he has been a spark plug for the offense all season when healthy and the team has been stagnant in his absence.

Despite missing the past 19 games entering Friday and playing in just 60 games overall, Chisholm still leads the team in slugging (.535), OPS (.860), home runs (14), RBI (45) and runs scored (39). He also has 12 stolen bases.

Roster move

The Marlins on Friday placed right-handed pitcher Cody Poteet on the 15-day injured list with right elbow inflammation. The IL designation is retroactive to Tuesday, meaning the earliest Poteet can be activated is Aug. 2.

This is Poteet’s second IL stint that has been a result of an elbow injury. He missed about six weeks with his first stint before being activated on July 15. Poteet made just one relief appearance after being activated, giving up five runs on seven hits (including two home runs) over two innings on July 16 against the Philadelphia Phillies.

Jordan Holloway replaces Poteet on the active roster. Holloway has a career 3.96 ERA over 14 MLB appearances (four starts, 10 in relief) but has pitched to a 6.08 ERA in the minors this season over 11 appearances (five starts) and missed more than two months with an injury.

Marlins sign second-round pick

The Marlins on Friday signed second-round pick Jacob Miller, the No. 46 overall pick in the MLB Draft.

Miller is an 18-year-old right-handed pitcher out of Liberty Union (Ohio) High School and was tabbed as the No. 37 overall prospect in the draft by MLB Pipeline.

He was Gatorade’s Ohio state player of the year after pitching to a 0.35 ERA with 94 strikeouts against six walks over 40 innings last season.

Over his high school career, he recorded 382 strikeouts over 172 innings pitched in 27 starts.

Marlins senior director of amateur scouting DJ Svihlik said the Marlins view Miller as a potential mid-rotation starting pitcher and noted the Marlins saw “a lot of his starts with our entire scouting staff this spring” and that Miller was a target of theirs for “multiple, multiple months.”

The 6-2 righty primarily relies on a fastball that sits between 91-95 mph but has touched 97, a 78-82 mph curveball and a 83-87 mph slider. He is also developing a mid-80s changeup.