Lopez was removed from Tuesday's game against the Nationals due to right shoulder tightness.
Lopez only managed to last one inning in Tuesday's contest, during which he allowed one hit and struck out one batter. His velocity was also noticeably down, and it now appears his shoulder may have had something to do with that. There's no telling at the moment if he'll require a trip to the injured list, though Atlanta may wait a few days to see how he recovers before making a decision.