The ES emini contract is currently trading down 13 points. Yesterday the $spx closed at a multiday low. Below is a equity curve of a strategy that fades down gaps when the previous day closed at a 15 day low. The strategy exits at gap fill or at end of day.
As you can see this would suggest a decent historic edge. Again, please note this set-up does not include factors such as seasonality, trend, gap size average drawdown etc, other factors that need to be considered. Please trade at your own risk.