Escobar said after the game that he felt OK and hoped to play Thursday, but the Royals sat him when he continued to show symptoms. The injury is not being declared a concussion yet because the data from the computer analysis is not yet complete.
"He's having some difficulty responding when he moves his head quickly up and down," manager Ned Yost said. "He's doing better than he was [on Wednesday], but he's not ready."
If Escobar's symptoms subside on Friday, the Royals' medical staff will exert him, then re-examine him. If he clears that procedure, he could possibly play on Saturday or Sunday.
It also is possible that he could be put on the seven-day disabled list retroactive to Thursday.
Christian Colon started at shortstop on Thursday.
Jeffrey Flanagan is a reporter for MLB.com. Follow him on Twitter at @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.