He was supposed to be hitting second and playing left field, but the Braves announced Upton was out of the lineup shortly before first pitch. Evan Gattis started in left for Atlanta, which lost to New York, 5-3.
"You get muscle tightness, things lock up," Upton said. "You just give it a little bit of time and it'll work itself out. Obviously, getting treatment and stuff like that, hopefully it feels better tomorrow. You just never know."
Upton is hitting .269 with 23 home runs and 62 RBIs.
"It about stayed the same. It hasn't gotten any worse," Upton said. "I imagine overnight getting some rest and coming back tomorrow and getting more treatment, it should be getting progressively better."
Chris Iseman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.