The Chiefs starting right tackle has been out for over two weeks with an undisclosed injury.
That changed on Wednesday when O'Callaghan returned to practice, according to Josh Looney of KCChiefs.com.
We're not sure what exactly O'Callaghan's injury was but it's possible the Chiefs held him out of the final two preseason games for precautionary reasons to prepare him for the regular season.
For now, it appears O'Callaghan will play. Todd Haley says that players generally have to practice to play so it's looking good for O'Callaghan.
This now means that Barry Richardson can revert back to his role as the swing tackle. It also means the Chiefs likely won't be calling in any offensive tackle reserves for this game.
We'll find out more on O'Callaghan's status on Thursday when the Chiefs release their first injury report of the season.