Taking advantage of space and time is a major focus of tennis coaching yet few statistical measures exist to evaluate a player's spatio-temporal performance in matches. The present study proposed the time to net as a single metric capturing both space and time characteristics of the quality of a shot. Tracking data from 2017 Australian Open allowed a detailed investigation of the characteristics and predictive value of the time-to-net in 33,913 men's and 19,195 women's shots. For groundstroke shots, the majority of men's and women's shots have a time-to-net between 200 and 800 ms. The expected time to net was found to vary significantly by gender, shot type, and where in a rally it occurred. We found considerable between-player differences in average time-to-net of groundstrokes when serving or receiving, indicating the potential for time-to-net to capture differences in playing style. Time-to-net increased prediction accuracy of point outcomes by 8 percentage points. These findings show that time to net is a simple spatio-temporal statistic that has descriptive and predictive value for performance analysis in tennis.