World number two golfer Day, who won the US PGA Championship in August, and his wife had courtside seats at Quicken Loans Arena and were helpless to avoid 6'8" James as he scrambled to keep the ball in play.
Day was put on a stretcher and taken to hospital with her neck in a brace before being discharged early this morning.
"She squeezed my hand, said she was fine. I think she was just a little weary," Cleveland.com quotes James as saying.
The incident occurred in the fourth quarter of the Cavs' 104-100 win over the Oklahoma City Thunder, which ended the longest winning streak in the NBA.