Why doesn't Caro hit more aces? Is she concerned/not confident in her 2nd serve if she gets in less 1st serves?
I was wondering about this partly due to the latest match stats the Wta put out which to my big surprise has Jankovic in the top 10 in aces for the year.
I really don't know. I guess all players would like to serve more aces - especially at crucial stages of the match (game point, SP, MP). An ace is a free effortless point, so to say, and might come in handy. But I'm not convinced the amount of aces has any significance at all. A player may serve a lot of aces and still have a terrible serve, while another player serving significantly fewer aces can have a much better serve. That's just my opinion, of course, but I'll try to elaborate (excuse the length and obviousness of the matter, but some might find it useful...).
The amount of aces are just statistical numbers or figures, and such statistics never tell the whole truth. Jankovic, for instance, is on that top 10 list, and Stosur isn't. But I would still argue, that Jankovic's serve is weak compared to Stosur's (and many other player's)! Jankovic has played a lot of matches in 2011 (16), which obviously increases her total amount of aces (one of the other players on the list has only played 7 matches, but still has more aces than Jankovic!). Furthermore, several of Jankovic's matches have been three-set matches, often with a 7-5 score in the sets, and she has also played several tie breaks this year. This, I believe, explains her relatively high total amount of aces. (Not to mention the stuff, we can't see directly: did she play many "love" games or many deuces in each game?).
Aces (and winners and errors for that matter) are nothing but numbers, and I'd like to take a completely different approach and discuss some other statistical aspects of serving. I'm sure there are a lot of obvious factors determining whether a serve will be successful or not (speed, angle, depth, spin/kick etc.). You all probably know more about that than I do. I guess the server's position at the serve line, the toss, and the body motion during the execution also plays a role - at least in how easy the serve is to anticipate for the returner. And most important, perhaps, is the willingness to go "all in" on the first serve, as you rightly suggests.
This also means, however, that serving many aces means serving with bigger risk (as summarized above), which again means a decreasing 1st serve percentage and therefore an increasing amount of 2nd serves! And since winning points on 2nd serve is much harder (for the server!), going "all in" on the 1st serves can be a dangerous route to go down! All of this is sort of implied in Protoss' quote, and I completely agree as to why Caro may seem reluctant to go "all in" on her serves. To prove my point I've made the table below using some of KleineBiere's excellent stats
(I hope you don't mind, KleineBiere!). The stats are from 2011, and include a few selected players appropriate for my purpose:
Aces per match Serve points won
Clijsters, Kim 1,8 61,9%
Wozniacki, Caroline 1,7 60,3%
Petrova, Nadia 5,1 60,1%
Hantuchova, Daniela 4,0 59,2%
Hercog, Polona 5,8 58,9%
Marino, Rebecca 8,1 58,7%
Ivanovic, Ana 5,4 58,5%
Kleybanova, Alisa 3,7 58,4%
Watson, Heather 3,8 58,0%
Safarova, Lucie 3,6 57,8%
Jankovic, Jelena 3,7 57,4%
Hradecka, Lucie 6,9 57,2%
Schiavone, Francesca 3,6 57,0%
Cornet, Alize 3,7 56,8%
Kanepi, Kaia 3,6 56,8%
Parra-Santonja, Arantxa 4,1 54,5%
Dokic, Jelena 3,8 54,5%
Amanmuradova, Akgul 4,0 52,2%
The two columns may seem completely unrelated, but there is a relation after all. The first column shows aces per match. I'll ignore the fact that this is not always a very useful statistic (cf. my discussion of Jankovic aces above), and keep it as it is, since this is a statistic often referred to. The right column shows serve points won - i.e. the percentage of points won on all serves (1st AND 2nd serve added together). This is a very useful statistic as it shows us what we really want to know. After all, winning points is what matters in tennis; not aces! And I'm quite sure that all the players on the list would prefer high "Serve points won" percentages over more "Aces per match"!
Notice that Clijsters and Wozniacki are winning more points on their serves than anyone else on the list. Notice also that all the other players on the list have averaged at least twice as many aces per match! Yet, Caroline and Kim win more points on their serves. They are better players, of course, and therefore more likely to win the point once it goes into rallying. But that's not the whole reason for their higher winning percentage. It's also because they don't go "all in" on their 1st serves, and therefore are able to maintain a rather high 1st serve percentage. You can't see these 1st serve percentages in the table above, but we know from KleineBiere's original tables that the average 1st serve percentage for Kim and Caro is 66.9% in the analysed period of time. For comparison, the other players on the list - let's call them "the good servers" - have an average 1st serve percentage of 58.7%. This means that the "good servers" more often must serve 2nd serves, which again means less chance of winning the point! It's a very delicate balance, but the best approach must be the approach that's winning (i.e. Kim's and Caro's).
Small print: I'll have to admit one thing before anyone accuses me for manipulating the stats! I've chosen a few players who fit my purpose, but I must also admit, that it IS possible to serve many aces AND have a high 'Serve points won' percentage! Stosur is one such player. Serena in grand slam form has always had that quality too (although there are no 2011 stats for her). There are a few others. So I'm not saying, that serving many aces is a bad thing. I'm only stressing the fact that serving many aces doesn't necessarily lead to a high 'Serve points won' percentage (which the table hopefully shows).
One last aspect, I need to mention, is service winners. Some players can serve excellent unreturnable serves, which are not real aces. Here are two such serves from Wozniacki (early in the match vs. Cibulkova at AO 2011):
There are two serves in the clip. Serve no. 2 was perhaps not un-returnable, and it was won via challenge as Cibulkova's return was too long. But it was a good serve that forced Cibulkovar far out in her forehand. Serve no. 1 was extremely good! If Wozniacki could serve like that all the time, then it wouldn't matter at all if she never served any aces. Unfortunately serve winner statistics is never gathered anywhere. It would be very useful though, and it would say a lot more about who's serving good and not...