The extra precautions the Mets are taking with Luis Robert Jr. might not be enough. Robert, following the team’s scheduled day off, was absent from the starting lineup in the Mets’ 8-0 win over the Nationals , and manager Carlos Mendoza revealed the outfielder is dealing with lower back tightness. Robert will be evaluated daily, but Mendoza indicated the injured list is a possibility. “Sunday, lower back tightness, that is why he played only one game,” Mendoza said, referring to the team’s doubleheader against the Rockies. “It didn’t get better. He is getting treatment as of right now.” Luis Robert Jr., who is battling lower back tightness, could be headed to the injured list. Robert Edwards-Imagn Images Robert’s injury history has dictated the Mets not pushing him too hard — including days when Robert’s only availability has been to pinch hit in a game-deciding situation, so he won’t have to play the field.…