Right now, the Rangers are listing Hamilton as "day to day." Hamilton, who has started all 22 games for the Rangers this season, had an RBI single in the first inning off of Rays starter David Price in Sunday's 5-2 loss to Tampa Bay. He is now hitting .395 on the season, with nine home runs and 25 RBIs.
"I'm not worried about it because I didn't feel anything alarming or anything like that," Hamilton said. "It was just a little tight this morning, but nothing out of the ordinary. I just came in and got loosened up and it felt great."
Hamilton said he felt a spasm in his mid-back after his single up the middle off Price. He later slid into second base on a fielder's choice groundout by Adrian Beltre for the second out in the inning.
"I made contact and I hit the ball, and about the third or fourth step out of the box, I felt my mid-back spasm up on me," Hamilton said. "I got to first and tried to stretch it out a little bit and it wouldn't release. I came back in and stretched my back underneath, and then I went out there and realized I couldn't really rotate like I wanted to. And I told Skip I couldn't go."
Hamilton, who started in left field for the sixth time, was replaced by David Murphy. The Rangers' next three games are on the artificial turf in Toronto and that could be some cause for concern for Hamilton.
He said he usually doesn't notice the effects until the third day playing on it, but he will get the benefit of the Rangers' off-day on Thursday. Hamilton said it could help him to be the designated hitter, as opposed to playing in the outfield.
"If I went out there and played in the field [on Sunday] and obviously it was affecting me," Hamilton said. "With a back spasm, it's tough to breathe and everything else."
Another concern could be the three-hour flight to Toronto on Monday morning -- the Rangers played a night game on Sunday to accommodate an ESPN national broadcast. Hamilton said he doesn't normally sleep on flights, and has been told by team trainers to get up and walk around every 30 minutes on the plane to keep his back from stiffening up.
Hamilton said he hopes a good night's sleep will get him in a relaxed state and help him feel better. He said he will reassess everything on Monday with team trainers when they get to the ballpark in Toronto.
"I've had it happen before," Hamilton said. "Very rarely. It usually takes about 12 hours or so, and it releases."
Todd Wills is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.