Assistant GM John Ricco told reporters on Wednesday that Wilmer Flores is dealing with a “disc issue” in his lower back.

The third baseman was placed on the disabled list on Monday after being removed from Sunday’s game against the Milwaukee Brewers in the fourth inning. No timetable was given for a potential return.

Flores, 26, is having a down year offensively but had been heating up before his injury. On the season, he’s hitting .248/.320/.398 with three home runs and 13 RBIs in 128 plate appearances.

Meanwhile, Ricco confirmed that Todd Frazier will be starting a rehab assignment this weekend, which could put him in line to return on Tuesday against the Baltimore Orioles.

The 32-year old was hitting .237/.357/.412  five home runs and 21 RBI in 112 at-bats before going down with a strained left hamstring.