Kerry Collins is still feeling the effects of a concussion suffered two weeks ago.
He's been limited in practice this week.
Painter started last Sunday's game against the Tampa Bay Buccaneers and will be getting his second NFL start.
Caldwell also said it is unlikely right guard Ryan Diem will play against the Chiefs (1-3) but that the Colts (0-4) had not yet ruled him out.
Diem has missed the last two games with a sprained left ankle and could move back to his old spot, right tackle, with the Colts' top two left tackles out this week.
John Clayton is a senior NFL writer for ESPN.com. Information from The Associated Press was used in this report.