Originally Posted by tennis_pro
It was a shot that led him to Madrid, FO, Wimbledon victories back in 2009. He kept using it in mid/late 2009 but with less and less frequency. Why do you think he switched back to his old game afterwards?
He didn't stop
using the drop shot 2009/2010. It's more like he started
using the drop shot circa 2011 to present.
Do you know what confounders are? Look that up in the dictionary. A book printed as in Freakonomics utilizes this principle that is a result of absentmindedness.