Robert is out of the lineup Tuesday against the Nationals due to lower-back tightness, Chelsea Janes of SNY.tv reports.
Robert's absence from the lineup is his third in the past four games, so it's not a surprise to find out he's managing an injury. The veteran outfielder isn't scheduled to undergo any medical testing at this point, but that could change if there's no improvement in the next 48 hours. For now, Robert should be considered day-to-day.