Ross took a foul ball off his mask on Wednesday in New York, and said he's had a headache, nausea and fatigue, and has been a little irritable since then.
"I was a little off a couple days ago -- I'm probably always a little off," Ross said. "It's hard to tell what's normal for me, to be honest."
The move was precautionary, and the Cubs selected the contract of catcher Taylor Teagarden from Triple-A Iowa.
"The main concern is getting another foul ball [off the head]," Ross said. "I had that happen a couple years ago, and it put me out two months.