Serena Williams talks to the media during the BNP Paribas Open in March, 2015.

It is rare air to get a whiff at completing the Grand Slam, but Serena Williams coming within three sets of completing the historic milestone might be the most heartbreaking of losses.

Williams saw her Grand Slam dreams come to an end when she was upset by the unseeded Roberta Vinci 2-6, 6-4, 6-4, which also saw Williams have an early break in the third set.

Twice, Williams has won four consecutive majors, including this year, which she’s dubbed the Serena Slam. But the true Grand Slam is winning all four in the same year, starting with the Australian Open and ending with the US Open. The last person to do it was Steffi Graf in 1988, a year where she also won the Olympic gold medal.

Had Williams won, she would have joined the exclusive sorority of Graf, Margaret Court (1970) and Maureen Connelly (1953) as the only females to do it in women’s tennis. On the men’s side, only Rod Laver (1962, ’69) and Don Budge (1938) did it.

Completing the true Grand Slam would have been an indisputable fact when people argue who the greatest tennis players ever were. This is why in some circles, Laver is still considered the greatest tennis player, because he’s the only player in history to complete the Grand Slam twice and the only male player to do it on the Open era.

Because Williams didn’t complete the Grand Slam, Graf and Court are the only females to complete the Grand Slam in the Open era, and Graf is the only one to do it on three different surfaces.

Who comes that close to a Grand Slam and loses it by three sets? That will be a tough one to swallow for Williams, who was so close from a historic achievement.

Williams has tried to talk down the significance of the Grand Slam, but judging by her brief post-match press conference, it disappointed her more than she wanted to let on.

Everything was set up for Williams as she would not have had to face a top-10 player in the US Open to the title. It was tailor made for Williams to complete the Slam.

Now everyone wants to make out that this is a huge upset in the ranks of Buster Douglas knocking out Mike Tyson, Villanova beating Georgetown in the NCAA final or the US Olympic hockey team beating the Russians. And maybe it is, as Vinci was only ranked 43rd coming into the US Open and never made it this far in a major.

But here’s a few things to consider as well: Williams has a habit of losing to unlikely players in big tournaments.

Since the start of 2012, Serena Williams has lost eight times in major tournaments, and the highest-ranked player she lost to was No. 14 Ana Ivanovic in the fourth round of last year’s Australian Open.

Her other losses have come to No. 56 Ekaterine Makarova in the fourth round of the 2012 Australian Open, No. 111 Virginie Razzano in the first round of the 2012 French Open, No. 25 Sloan Stephens in the quarterfinals of the 2013 Australian Open, No. 24 Sabine Lisicki in the fourth round of the 2013 Wimbledon, No. 35 Garbine Muguruza in the second round of the 2014 French Open, No. 24 Alize Cornet in the third round of Wimbledon. Vinci is ranked 43rd heading into this year’s US Open.

There is another perception of Williams that appears to be misleading. While Williams has completed her second “Serena Slam,” winning four consecutive majors, she has been anything but dominant.

In the Serena Slam from 2002-03, Williams lost four sets. This year, Williams lost five sets in the French Open alone, and a total of nine during the Serena Slam. At the US Open, Williams lost four sets (one of Bethanie Mattek-Sands, one to Venus Williams and two to Vinci).

It has been an exceptional year for Williams, but not as dominant as she can be.

The first Serena Slam was so much more impressive if you look at the depth of the women’s game, particularly at the top. During the 2002-03 Serena Slam, Williams defeated the likes of sister Venus in all four finals, but also Hall of Fame players Lindsay Davenport, Martina Hingis, Mary Pierce, Amelie Mauresmo, Jennifer Capriati and Kim Clijsters. Another Hall of Fame player in that era was Justine Henin, who ended Williams’ Grand Slam winning streak in the semifinals of the 2003 French Open.

During this Serena Slam, Williams only beat three players ranked in the top-10, and two of those wins were against Sharapova.

What made this Serena Slam so remarkable is that Williams did it on grit. She was big in the big moments, to pull out some amazing wins. And to do it at 33-years old (actually 32 at last year’s US Open which started the Serena Slam), that is a pretty remarkable outcome and a tribute to her longevity.

But coming into the semifinals against two players she had never lost to, and up a break in that third set against Vinci, this might be a loss that Williams will never be able to forget.