THINGS have been known to go awry for Serena Williams at the US Open.

Twice in the last three years she has suffered the sporting equivalent of self combustion here; threatening to shove a tennis ball down a line judge's throat in 2009 following a semi-final foot fault when match point down, then abusing a chair umpire who penalised her for premature celebration during her 2011 final defeat by Sam Stosur.

Unfortunately, for the remainder of the tournament, everything currently appears to be sunny in Serena's world. The 30-year-old has made her way to a 22nd Grand Slam semi-final today without so much as a semblance of fuss. She is the only one of the four semi-finalists to have arrived in the last four without dropping a set, and so untroubled has she been on her route through this tournament that it seems a pretty fair bet that she could lift the title without doing so.

Serena meets Sara Errani, the French Open runner-up today, but although Errani has had a great year and proved herself the pre-eminent Italian in the draw, it wasn't too long ago that she was humbled by being on the receiving end of Yaroslava Shvedova's 'golden set'. You fear for the 25-year-old from Bologna – now the pre-eminent doubles player in the world – amid the onslaught she is sure to face today.

"She's a great fighter and has a great attitude," said Serena. "When you have such self-belief in yourself then you can do anything. I love her attitude. I'm inspired by it actually. But I feel like I'm going to get more focused and serious and start playing Serena tennis in the next couple of rounds, if I get to play two rounds. I have two matches left and I am going to give 200%."

By the peculiar logic of the WTA tour, whatever happens in the remainder of this event Serena will move no higher than fourth in the rankings. But she has won all three of the meetings with Errani to date and, assuming she gets through again, she will face the winner of the Russian battle between Maria Sharapova and Victoria Azarenka.

The Belarussian just shades the head-to-head, having won five of their nine meetings, but this is a match-up with an edge between two American-based players both of whom have a 2012 major win under their belt. It is doubtful Serena will lose too much sleep over either, however. She has won nine of her 10 meetings with Azarenka and nine of her 11 meetings with Sharapova.