Originally Posted by abmk
actually , by my stats
32 UEs in 133 rallies in the semi (24.06%)
49 UEs in 206 rallies in the final (23.8%)
referring back to your post :
if we make murray's return % to 56, it comes to 72 returned serves out of 128 rather than the actual 99 out of 128 ... so difference is 27 serves , not 17 serves ...
if we make 20-21 accounting for fed's superior serving in the semis...... no of UEs produced by getting more returns into play ~ 5
earlier calculations for AMs:
federer : 31.95%
djokovic : 26.4%
federer's AM = 29.5%
murray's AM = 24.7%
if we 'remove' these 5 UEs
federer's AM = 31.25%
murray's AM = 26.4%
that brings the AMs in these matches very close ...
having said that murray's superior returning on the first serves doesn't seem to have as much of an effect on the no of UEs as I initially thought ....
perhaps better returning of 1st serves has more of an effect on slower surfaces where % of UEs per no of baseline rallies is more !?
Yes, since you gave more UE's to the semifinal than Wimbledon.com did, your AM's for the two matches are already very close. And the AM's would be even closer in the hypothetical scenario in which Murray returns only as well as Djokovic did, and we drop 5 UE's from the final -- but I think there are a few problems with that last step.
In your stats Murray made 4 fewer UE's on the return than Djokovic did. And if we're asking how many of the total UE's in the match resulted from Murray's superiority over Djokovic as a returner, those 4 fewer UE's have to be accounted for.
So if Murray's extra returns in play added 5 UE's to the final, his returning also took away 4 UE's. For all intents and purposes that cancels out any effect on the AM's, as far as Murray's extra returns go.
And the UE's that Murray avoided making on 4 points, at least in your count, are certain; the 5 UE's that he added over the course of the match by getting extra returns in play are hypothetical. Most of those extra returns would have been on serves that normally caused forced
errors, rather than UE's (that has to be true because the vast majority of the return errors in the match, by anyone's count, were forced).
So I go back to the arguments I made above. If the receiver gets a tough, forcing serve back into play, a common result is for the server to be shocked or thrown off balance, and forced into an error. We're extrapolating our UE's based on the total % of rallies that ended in UE's, but a rally that starts with a tough serve unexpectedly returned is not a typical rally. The % of such rallies that end in UE's could be very different from the overall %.
So the 'extra' UE's produced by Murray's returning could be 5, or perhaps only 2 or 3. And Murray avoided making UE's himself on 4 returns: so I think even going with your numbers it's a very difficult argument to make, that better returning can produce lower AM's.
As far as slower surfaces, as you say, the % of UE in rallies is larger. So hypothetically a receiver who gets a lot of tough first serves back into play can end up inflating the total number of UE's in the match.
However, the same objection there: on slow surfaces, serves do not force errors the way they do on fast surfaces. And the players themselves don't necessarily serve all-out the way they do on fast surfaces. There are more opportunities to make UE's on the return. So a player who displays superior returning skills should also be reducing the UE's in a match when he gets easy/moderate serves back into play, thus raising the AM's.