I can not believe you think Keane left his man to head the ball away and misjudged it. He left his man BECAUSE of the player who drifter away from Gana and into the gap between holgate and Keane.
Keane is tight to Jimenez here, he's got his hand on his arm so he knows where he is. Look where the ball is. It's already travelled, what, 10-12 yards? At this point there is no chance whatsoever that the ball is going to the player in front of him, and yet it's after this that he leaves his man. Either he was going to the man in front of him because he had
badly misjudged the flight of the ball - by about 10 yards - or he was trying to head it clear because he had
slightly misjudged the flight of the ball - by about a foot - but either way, he clearly misjudged it.
The fault lies with others for not stopping the cross, Holgate is also asleep and doesn't even appear to have noticed the player running into the box, but to try and suggest Keane had no option but to do what he did is absolute nonsense. That cross cannot reach the man at the front post because of the angle of the ball and the run, he is of no danger in this situation, so if Keane went with him and ignored what was obviously the greater danger (the proof was in the pudding) then he's made a massive ricket. Personally I don't think he did, I think it was just a good ball and a momentary lapse which allowed his man to get away from him. It happens.