The Black Cats were offered the opportunity by sponsors to be guests at the racing event but having taken just one point from the last 18 available in the Premier League, the players decided against attending, something that O'Neill admitted was the right action to take.
"The lads had thought about going down there, and I'm quite sure had we eked out a win against QPR then they probably would have gone," O'Neill told the Sunderland Echo.
"But in the grand scheme of things I think the priority is clear and that is the overwhelming need to win some football games, hopefully starting this weekend and to do that, the focus has to be be total."
"The Cheltenham thing was straightforward."
Sunderland are currently 16th in the Premier League.