Johnson was seen walking around the ballpark after Friday's 6-4 loss to the Angels with a heavy pack on his lower back, and reported the issue hadn't subsided completely when he arrived Saturday.
Treatment during Saturday's game apparently did not do much to calm the issue, and manager Joe Girardi now expects that Johnson will remain sidelined until at least Tuesday at Baltimore.
"Sometimes you come in and believe if you get in the whirlpool and get a little more treatment, it's going to loosen up," Girardi said. "It doesn't and he was honest about it. He said it was stiffer."
Johnson said that he felt the stiffness during batting practice Friday but played anyway. He was in a 0-for-21 funk before singling in the fourth inning off Ervin Santana.
"I felt a little something and decided to let it calm down," Johnson said. "It didn't hinder anything, but I'm trying to be smart about it."
Johnson also had an issue with back stiffness this spring when he caught a spike on a turf mat around the batting cage. He said that this latest bout was in a different, lower spot.