“Points won on 1st serve” is supposed to be a measure of 1st serve effectiveness. It’s not officially labeled that way, but that is precisely what it’s supposed to represent. The more points you win when your first serve goes in, the more effective your first – or second – serve is.

But is it really a good measure of first serve effectiveness? 

The problem with “percentage won on first serve” is that it doesn’t make any distinction regarding how a point was won. In pro tennis, that makes a difference. In junior tennis, it makes a massive difference.

Consider these 3 scenarios:

1. Player serves a first serve wide to Deuce, gets a half-court response which they put away into the open court. 3 shot rally. Done.
2. Player serves a first serve and the ensuing rally lasts 13 shots, with the server hitting a forehand volley to the open court to win the point.
3. After a great return of a first serve and a deep shot 4, a returner hits a forehand unforced error from mid-court.

In all 3 examples, the server wins the point, but only in example 1 does the server win the point because of their first serve. In the second example, the point was won after a 7+ rally, which is to say the first serve was highly unlikely to have been the reason the player won the point. In the final example, you could argue that the first serve was ineffective because the returner had the opportunity to put an easy ball away on shot 6. 

Some out there in tennis land might argue that points 2 and 3 don’t happen as often. While true, it still means that, as a measure of first serve effectiveness, “points won on first serve” is full of irrelevant data.

The problem is compounded by the fact that points 2 and 3 happen more often in junior tennis than in pro tennis.

If we’re going to teach young players about the effectiveness of their first serve, it can’t be with shallow analysis like “points won on first serve”, because it says nothing about how the point was won (or lost).

A better measure of first serve effectiveness is to measure a player’s ability to win the point on shot 1 (the serve) or shot 3 or shot 5 in the rally, because it’s almost certain that winning the point on any of those rally length numbers is because of the player’s first serve.