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Old 01-16-2013, 09:44 AM   #130
Join Date: Dec 2006
Posts: 5,531

Originally Posted by abmk View Post
no ...... its the other way around ... I'm saying there is more chance of UE in the 'whole' point when net rusher is following an approach rather than his serve ...please read what I wrote again ...

yeah, I know you were trying to exclude the net points from baseline rallies .....

But like I said, I was talking about errors in rallies, not just @ the baseline ....

my argument was that there were more returns in play in the finals and most of the net points were NOT SnV in the finals, therefore that leaves ample scope for UEs in all those points ... ( including rallies at the baseline and those points that were constructed from the baseline and ended up in a net approach )
I see now that we were referring to different things. When I say that net play reduces the chances of an unforced error, I mean that if we looked at the final strokes that ended a net point, we would be less likely to find UE’s there than if we look at the final strokes of baseline rallies. So I presume that if we look at all volleys made at the net, we’re not going to find more volley UE’s behind the serve than we will find volley UE’s behind approaches.

What you meant by chances of an UE is the potential for an UE to occur if you’re just thinking of the two players as they begin their point: if they get into a long baseline rally there’s a great chance that they’ll end up making an unforced error; and there’s also a potential if they’re trying to get to the net, but less so, because those points might be shorter; and there’s the least chance of all for an UE to occur if the server decides right away to follow his serve to net.

It’s an interesting argument, and I see the logic now: Murray, by returning better than Djokovic, put more balls into play -- and once the ball is in play the point might end in an UE (at net or the baseline). Therefore the Murray final had a higher number of UE’s than it would have had if Murray had returned as “badly” as Djokovic, who often could not get the serve back in play. The higher UE’s meant lower AM’s than those of the semifinal.

However I’ve worked out the numbers, and I think Murray’s superiority in the service returns -- if it was responsible for producing any UE’s -- cannot have produced more than 2 or 3 extra UE’s.

The Murray/Fed match needs to drop more than 2 or 3 of its UE’s. It would need to drop 22 of its unforced errors, in order to equal the AM’s of Fed/Djokovic.

Okay, let me say this about your argument. I do not think it can work if we’re talking about Murray returning better than Djokovic because he made fewer UNFORCED errors on the return. I said this above to Burstyn: if a player is cutting down his UE’s on the return and putting more balls into play, he is lowering the UE’s of the match as a whole, and the AM’s will rise. That’s not the problem with Murray/Federer: we’re looking for a way to explain how Murray’s returning might have ADDED to the UE count and lowered the AM’s.

But I can see how your argument might work if Murray’s better returning cut down on the number of FORCED errors. You mentioned that yourself in a post above: if Murray is able to return the kind of powerful serves that forced Djokovic into return errors, then he’s putting the ball back into play without decreasing the # of UE’s in the match: and those extra rallies might end in some UE’s. Thus adding to the UE’s of the match as a whole.

(I don’t think the argument really works for Djokovic/Fed/Murray, but I’d like to apply it to matches between HUGE servers who have a weak overall game and who can be counted on to make unforced errors if you can only get their huge serves back in play. But I’ll leave that for another post.)

I concede that Murray’s strength on the return does happen to be his ability to get serves back in play. Maybe Djokovic has the more aggressive return: but Murray got more of Federer’s serves back in play. We’re talking about big, forcing serves: not the kind of serves on which the receiver can make an UE trying to return it. Murray and Djokovic actually had nearly identical numbers, as far as UE’s on the return (those numbers available on the Wimbledon site). It’s on the big, forcing serves that Murray must have done better than Djokovic.

So in a way this is a perfect test case.

The main problem is that Murray cannot have put nearly enough serves back into play -- not nearly enough to account for the difference in AM’s between the final and the semifinal. He needed to put enough serves back in play for 22 EXTRA unforced errors to appear. And since only a fraction of rallies end in unforced errors, you can imagine that the number of EXTRA rallies that he needed to create would be far more than 22.

In the actual matches, the number of powerful serves that Murray put back in play -- serves of the kind that Djokovic could not return -- was probably somewhere around 10 (I’ll show that below). And only a fraction of those -- if any -- would be likely to end in UE’s.

You can easily find out the number of rallies (baseline or net) in these matches (Total Points minus Unreturned Serves minus DF’s).

And you can find out the number of UE’s that occurred in the rallies (Total UE minus DF’s minus UE’s on the return).

Semifinal -- 133 rallies, of which 6 ended in UE’s (5%)
Final -- 206 rallies, of which 35 ended in UE’s (17%)

So of the extra rallies that Murray created with his return, you’d have to say that only about 17% of them were likely to end in UE’s.

And how many extra rallies did Murray probably create? Well if you lower his rate of “Returns In” to make it exactly equal to Djokovic’s (56%), you’d give Murray 17 more return errors. So is 17 the number of extra rallies that Murray’s quality return created? Not quite, because we agreed that Murray had weaker serves to deal with than Djokovic did (Novak faced higher MPH from Federer). So that’s why I said 10 before. As a compromise. Ten extra rallies produced by the quality of Murray’s returning.

And 17% of 10 extra rallies comes to 2 extra UE’s.

That would increase the combined AM’s of the final by less than 1%.

So I think if the AM’s of the final are lower than those of the semifinal, we’re looking at two possible causes:

1) the level of play in the final was genuinely lower
2) there is a discrepancy in how the UE’s were scored in these two matches
3) the AM method does not describe these two matches very well

(#2 and #3 may be related)
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