Too much is being made of the "mistake" on Saturday. He slipped and was maybe a yard out of position because of the unusual direction change of the ball. That exact thing happens hundreds of times in football, it's very unfortunate to concede from it.
The mistake last week was awful, there's no escaping that, but he recovered and had a solid 2nd half.
The problem with all of this is Keane, when he is on form and not in his own head, is a very good centre half. But he has massive fluctuations in confidence and you have to hope it doesn't lead to further errors if his head drops.
Personally, I'd keep him in with Mina as they make the best partnership. Everyone goes on about Godfrey, but most of his best performances have come at left back, and starting him for his 1st game of the season after what we can assume is due to isolating away from the squad, to create our 3rd centre back partnership in as many games, is not what a team looking for stability should be doing.