CLEVELAND -- The Indians announced Thursday that Leonys Martin was placed on the 10-day disabled list with a "non-baseball condition," making the newly acquired outfielder the latest to miss an extended period of time.

The ailment held Martin out of the lineup Wednesday against the Twins, but the eight-year veteran could "potentially" be out longer than 10 days, according to president of baseball operations Chris Antonetti. Antonetti also said because the injury wasn't baseball related, he couldn't share specifics or whether or not Martin is currently with the team.

"We're not quite sure yet how long he'll be out," Antonetti said. "It happened really quickly. After the game the other night, he just didn't feel well. … We're now in the process of kind of getting him assessed and working through the best way to get him healthy."

Replacing Martin on the 25-man roster is outfielder Greg Allen , who was recalled from Triple-A Columbus.

Since Martin was acquired from the Tigers on July 31, he's hit .333 (5-for-15) with a 1.086 OPS, two home runs and four RBIs in six games, starting four. The 30-year-old is hitting .255/.323/.425 through 84 games in 2018.

Martin is the fourth Indians outfielder capable of playing center field on the DL, along with Bradley Zimmer (right shoulder surgery), Lonnie Chisenhall (60-day DL/left calf strain) and Tyler Naquin (10-day DL/right hip surgery).

"Our depth has definitely been tested," Antonetti said. "It's afforded us the chance to give guys some opportunities to play. And now Greg will be back up here, and he'll have an opportunity to continue his development and progression here at the Major League level, while contributing to help us win games. But it's been an area where there's been a lot of instability over the course of the season."

Of the aforementioned, Antonetti said Chisenhall -- who's been sidelined since July 3 -- is the only player expected to return by the end of the regular season. Naquin, who was projected to be out six to 10 weeks as of last Friday, is still "undetermined" if he'll be available.

"Some of that will be dependent upon just how quickly he gets through the initial phases of the rehab process," Antonetti said of Naquin. "So he'll be right there at the edge, if he's available or not."

Allen, a rookie, has spent most of the season with the Clippers, but he has appeared in 47 games for the Indians. In four Major League stints this year, he's hitting .224 with four doubles, two triples, a homer and six stolen bases. With Columbus, Allen has a .298/.395/.409 slash line with 15 extra-base hits, 14 RBIs and 12 swipes. Allen last played with Cleveland on July 31 before Martin was acquired, and he hit three singles in a 6-2 win on the road against Minnesota.

"Greg's done a great job," Antonetti said. "I think he's really focused on continuing to improve as a player wherever his feet are."

Even though the July 31 non-waiver Trade Deadline has passed, Antonetti said the front office is still doing its due diligence in searching for roster upgrades. Teams can still complete trades in the month of August, though it gets a bit complicated. In order for players to be acquired, they must clear waivers and be claimed by the Indians in order to further negotiate a trade.

"I will say more broadly that we'll continue to spend the month of August looking for opportunities to improve our team," Antonetti said. "What impact Martin's condition or illness has on that, we're not yet sure."

Tomlin working his way back

Right-hander Josh Tomlin pitched three shutout innings, allowing one hit, no walks and three strikeouts Wednesday in a Minor League rehab assignment with Double-A Akron. Tomlin has been sidelined since July 10 with a strained right hamstring, and he began his assignment with Triple-A Columbus last Friday, in which he allowed three runs, two homers and six hits in two innings.

"His velocity was ticking up, and he felt pretty good about his mechanics," Antonetti said. "His body felt good, so hopefully he's on a good path, and now we can continue to build up volume for him. Last night was an encouraging step."