Today’s women’s semifinals have at least one thing in common. In both, one player has yet to drop a set at the US Open and has lost many fewer games than her opponent.
Does it matter?
The differences are particularly glaring in today’s second semifinal, between Serena Williams and Na Li. Serena has not lost a set, and has dropped only 13 games. Li has been pushed quite a bit further, losing 31 games in her first five matches.
Out of 714 Open-era Grand Slam semifinal matches, 30 have featured two players with such a wide gap. To quantify it, we’ll note that Li has lost 2.38 times as many games as Serena has. Of those 30 matches, the player who had displayed more dominance in the early rounds won 25.
Strangely, though, the connection has been much weaker in recent years. Most of those 25 super-dominant semifinals were the usual suspects in WTA history: Margaret Court, Chris Evert, and Steffi Graf. Only five of these lopsided pairings have taken place since 1994, and of those five, the less dominant player has won three. The most recent example was Li’s semifinal in Australia. She went into her match having lost 31 games, while her opponent, Maria Sharapova, had lost only 9. Despite showing so much more weakness in the early rounds, Li won her semifinal 6-2 6-2.
In general, however, the more dominant the early rounds, the better chance a player has of reaching the final. Of the 349 Slam semifinals in which one player had lost fewer games in her first five rounds, 228 (65.3%) advanced to the final. The same percentage applies to the player who lost fewer sets en route to her semifinal.
Despite her low ranking and her buzzsaw of an opponent, this bodes well for Flavia Pennetta, right?
Well, not exactly. As hardly needs mention, there are other factors involved here. A great player might have a sloppy early-round match or suffer an unlucky draw. That doesn’t mean she’s any less great, or less likely to show her top form in the semis. Victoria Azarenka has certainly had a more challenging tournament so far than Pennetta has, but it would be a mistake to read too much into that.
For the most part, early-round dominance and superior WTA rankings go hand in hand. Of 228 semifinal matches where I have ranking data, just over half (117) were won by the player who had dropped fewer games–who just happened to be the player with the better ranking. No surprises here–if someone is going to play like Serena has so far, she’s probably #1.
The remaining 111 matches are where things get interesting. In 75 of them, one player had the higher ranking (like Azarenka) and the other had been more dominant in the early rounds (like Pennetta). The results favor the higher-ranked player, but not as much as you might expect: 30 of those 75 (40%) went in favor of the lower-ranked player.
Of course, most of those lower-ranked players aren’t quite the underdogs that Pennetta is. As we saw yesterday, Flavia is one of the lowest ranked semifinalists in women’s Slam history. Only two players outside of the top 32 have ever advanced to a final–Venus Williams at the 1997 US Open, and Serena at the 2007 Australian. Whatever else you might say about the Italian, she’s not a Williams sister.
Using these two variables, though, it is Na Li who faces the tougher challenge today. She’ll need to beat a higher-ranked player who has been untouchable through five rounds. Keep the faith: That’s exactly what she did in Melbourne this year.