Originally Posted by Bursztyn
Comparing success on first and on second serve we have to bear in mind that samples sizes should be more or less the same (that is the number of first/second serves successfully executed during a match). Usually this is the case however sometimes (as Wilander Leconte, FO 198
, players may have unusually high percentage of first serves in (Wilander 97%), which implies that the number of second serves executed was very small (2), and calculated success on second serve (50% in this case) is not very informative. Of course in that match Wilander success on first serve was higher that on the second serve.
Right, if you change just one point in Wilander's match he would have had 100% success on second serve. The comparison with first serve in that case would be flawed. However, as you say, his success on first serve was pretty high (70%), higher than most success rates on second serves.
I don't know if I would say that the sample sizes of first and second serves should be more or less the same. Not if what you mean is a first-serve percentage of around 50%. I think a player could make around 70% of his first serves and you'd still be left with a sizable number of second serves.
But I think you're raising an interesting point, and it might be worth looking at whenever someone makes more than 80% of their first serves, and certainly when they make more than 90%. The sample of second serves might be quite small.