New York Mets All-Star shortstop Francisco Lindor will undergo an MRI exam and other tests on his ailing back Monday after leaving Sunday’s game against the Philadelphia Phillies in the second inning.Lindor departed Friday’s game due to lower-back pain and sat out Saturday for his first missed game of the season. He attempted to play on Sunday and singled to lead off the game, but his movement was limited while fielding a grounder in the bottom of the first.Lindor asked to be replaced at the end of the inning. When the Mets took the field in the bottom of the second inning, Luisangel Acuna went out to play shortstop.”It’s extremely difficult,” Lindor said of leaving the game. “I’m somebody who wants to post up and be available as many times as I can. It is difficult to come out of the game. It is difficult to not be there for my teammates, not be there for my coaches and play the game that I love. It doesn’t feel good.”Mets manager Carlos Mendoza is trying to remain optimistic while waiting for answers.”It’s early to sit here and say I’m really worried,” Mendoza said. “We’ve just got to see how he feels tomorrow and the next day. It’s too early to tell.”