The 23-year-old Canadian-born striker scored the third goal in an American rout of Canada in Toronto, then proceeded to taunt the home fans.
A Canadian born-and-bred talent, Leroux put the final dagger into Canada by scoring the third American goal of a 3-0 U.S. victory.
That she scored wasn't much of an issue -- Leroux is a rising star for the world No.1-ranked American side, after all -- it's what she did immediately afterward that ruffled more than a few feathers at BMO Field.
The Surrey, B.C. native, who had been the subject of the crowd's scorn from the moment she stepped onto the pitch as a second half substitute, decided to 'shush' the most vocal of the Canadian fans while also pointing to the USA badge on her jersey.
That act brought about instant reaction, both in the stands and on the live broadcast. Former Canadian national team goalkeeper Craig Forrest, working the Sportsnet telecast as a colour commentator, took LeRoux to task for her "classless" display.
The reaction was just as harsh online, where colourful insults were hurled at Leroux's Twitter account just seconds after her goal nestled in the back of Erin McLeod's net.
The reality is, in Canadian women's soccer circles, everyone has an opinion on the 23-year-old. Most are not too kind, given that Leroux spurned Canada as a youth to join the U.S. program in what is widely seen by observers north of the border as a cynical move by the player for more opportunity at glory.
Leroux had starred in her native British Columbia as a teenager and even suited up for the Red and White a couple of times before permanently hitching her wagon to the American system in 2008.
With all of that in mind, Leroux's goal celebration brought about a nearly deafening chorus of boos from the BMO Field crowd. It wasn't exactly an unexpected reaction, from either side.
"I think her response was probably a reaction to the reaction of the crowd to her when she came on the field," U.S. head coach Tom Sermanni told reporters after the game. "To be honest, I think that's terrific."
Canadian coach John Herdman was diplomatic in his response, choosing to focus on Leroux's considerable talent rather than her taunting goal celebration that he never actually saw.
"I didn't notice it, I think I was kicking a water bottle at the time," Herdman said with a laugh. "I'd love Sydney to be playing for Canada, wouldn't you? Imagine her playing up front with [Christine] Sinclair and [Melissa] Tancredi, that would make a big difference, but she's not.
"So I think we've just got to let it go. Let it go, let her enjoy her time in the U.S. and just respect her as a player."
Of course, soccer supporters aren't really about "letting it go," and Leroux -- who has dealt with angry Canadian fans for years -- felt her actions were justified.
"Yeah, that stuff gets me fired up, obviously it's very different for me, considering I was born here, but I'm very happy," she said. "I've scored in the Olympics and it felt good and this one's up there, especially just because of everything that's kind of happened and all the boos and stuff. It was icing on the cake."
For her part, Leroux was complimentary on the passion of the record-setting BMO Field crowd, but she still hopes that she can play in Canada one day and not be the target of so much scorn.
"It's been quite a few years and how many American-born players do you have on Canada? I don't think there's any issue when Canada comes to the U.S.," she explained. "I think I dealt with it pretty well and I scored a goal and it made me that much happier."