The real effect of Federer's sneak attack return

In August 2015 Roger Federer began returning second serves from inside the service line, taking the ball on the half-volley and following it to the net, a tactic that became known as the Sneak Attack By Roger (SABR). Its effectiveness was debated at the time but never measured. We use shot-by-shot charting data from 358 of Federer's professional matches between 2010 and 2021, 22 of them in the four months of 2015 in which it was used systematically, to answer three coaching questions: how often it was used, whether it won points, and what opponents did in response. Under three operational definitions of increasing breadth, the tactic accounted for 6 to 12% of Federer's second-serve returns between the Cincinnati Masters and the Tour Finals, compared with 0 to 7% in the preceding eighteen months and 0 to 4% afterwards. In that period the tactic won 45 to 48% of the points on which it was used, against 46% on his other second-serve returns, and his return points won overall did not change. Opponents’ second-serve placement changed instead: the same twelve servers directed 28% of second serves at the body when serving to other players and 18% when serving to Federer, and 35% wide against 48%, while their first-serve placement to him was unchanged. No other aggressive returner in the charted record, including those who copied the tactic occasionally, produced a comparable response. The effect of the tactic was visible in the opponents’ game plans rather than in the returner's points.