The New York Mets placed starting catcher Francisco Alvarez on the 15-day injured list with a left thumb sprain on Saturday.Alvarez, 22, appeared to sustain the injury in the second inning of the Mets’ 9-4 victory against the Los Angeles Dodgers on Friday. While running the bases, he stumbled while going around first, then planted his left hand in the ground to stabilize himself before continuing to second base.The team scheduled an MRI exam.Manager Carlos Mendoza knew after the game he’d lost his starting catcher even before the diagnosis.”I’m pretty concerned, I’m not going to lie,” Mendoza said. “He was in pain. I am worried about that.”In a corresponding move, the Mets selected catcher Tomas Nido from Triple-A Syracuse and designated left-hander Kolton Ingram for assignment.