The obstacles are worthy adversaries, but only Serena truly stands in the way of her attempt at a rare calendar Grand Slam

NEW YORK – If flawless narratives played out in flawed real life, Serena Williams versus Venus Williams would have been the US Open final, with Serena’s calendar Grand Slam at stake and the sisterly drama playing out before a star-studded New York crowd to decide it all.

Venus is the opponent Serena most fears, the one against whom she still cannot summon up the full level of in-your-face emotion she sometimes needs to get over the finish line when her nerves get the better of her.

Instead, it was only a quarterfinal – a compelling one, but still two matches shy of the finale. Still, Williams showed more fist-pumping emotion than you usually see when she plays her big sister. “It's probably the toughest match I have played in a really, really, really long time where I wasn't actually beating myself. I was out there facing an incredibly tough opponent,” Williams said when it was done and dusted.

That perfect narrative also would have had Simona Halep versus Victoria Azarenka, the rain-interrupted dogfight played Wednesday and arguably the best match of the women’s event so far given what was at stake, meet in the semis for the right to play Williams and try to stop her quest.

Instead, it was only a quarterfinal.

Before the tournament, world No. 2 Halep said she wanted Serena to complete her historic 2015 effort. But if she got to the final, the Romanian was rooting for herself.

If the scrappy Azarenka, one of the few players who has genuine if not unshakeable belief that she can beat the world No. 1, can’t be there, a Williams vs. Halep final has the most potential.

It may happen. It likely will happen. Unless there is some major drama to come in Thursday’s semifinals – weather permitting, and the forecast is ominous – 32-year-old Roberta Vinci and 33-year-old Flavia Pennetta are merely the final obstacles on that path.

Draws only occasionally shake out for maximum dramatic effect. They almost never shake out in a way that ends with two 30-something Italian veterans in the semi-finals. But that was reality this time around.

To complete her calendar Grand Slam, the first in women’s tennis since Steffi Graf did it in 1988, Williams must first defeat Vinci. That’s something she has done four times in four attempts on three different surfaces, most recently in straight sets last month in the quarterfinals of the Rogers Cup in Toronto.

Then, Williams would have to get through either Halep or Pennetta, ranked No. 26 and a surprise semi-finalist here for the second time in three years.

Pennetta’s road to the semis was fairly legit. She didn’t have to play Caroline Wozniacki in the third round after the No. 4 seed lost to unseeded Petra Cetkovska of the Czech Republic. But she upset the higher-ranked Samantha Stosur in the fourth round and on Wednesday, defeated No. 5 seed Petra Kvitova 4-6, 6-4, 6-2 on another tough day for the two-time Wimbledon champion in New York.

The heat and humidity, very much in evidence here this year but always present at the US Open, got to Kvitova once again. Having to deal with mononucleosis this spring and summer, with the resulting drop in practice time and match toughness, didn’t help.

Vinci’s road was easier. You could probably call it a Genie Bouchard draw, 2014 vintage. Unseeded, she could have faced anyone in the first round, including Williams. Instead, she got Vania King, Denisa Allertova and Mariana Duque Mariño in the first three rounds. Top-10 player Carla Suárez Navarro and former US Open finalist Jelena Jankovic were in her path, but they were cleared away before she got there.

Then came the free pass from Bouchard in their fourth-round match after the Canadian’s incredibly unfortunate mishap in the women’s training room Friday night.

In the quarterfinals? Unseeded Kristina Mladenovic of France. You couldn’t write it up better. It’s Vinci’s first career Grand Slam semifinal, but she would have been furious with herself if she hadn’t made it.

She steps up about five weight classes on Thursday, figuratively speaking.

The 3-1 head-to-head in Pennetta’s favour over Halep is somewhat misleading. The Italian’s first win came on clay when Halep was just out of the juniors. One came on a retirement. The third came during Pennetta’s run to the semis here two years ago, in the round of 16.

The last time they met, Halep won in two close sets in Miami back in March

Williams was complimentary of Vinci when asked about her, saying she had a surprisingly tough match against in Toronto but also mentioning she sprained her finger in that match. She also said she now had a good idea of what to expect.

In the end, the most telling comments from the world No. 1 were about rivalries, about her toughest opponents.

None of the remaining obstacles to Williams’s career-crowning calendar Grand Slam were mentioned. Quite frankly; none of them deserve to be in that conversation – at least not yet, in the case of Halep. It's no knock on them, merely a reflection of the current era, a quality era in which Williams simply stands head and broad shoulders above the rest.

"I saw the match Serena played with Venus, and I just felt that she's more focusing than she did before, the matches before, and I think that she's kind of the player who with the tournament she's playing better and better every match," Kvitova said. "So I think that if she gonna be in the final, I think she's gonna put everything what she has inside and she's gonna win it."

If it's a Williams-Halep final, at least the Romanian has given Williams a quality fight before finally succumbing. But unless she’s beating herself – and we’ve certainly seen how disastrous that can be – any other narrative than the one that has Williams holding up the trophy, and four fingers, on Saturday would be, well, imperfect.