This Monday morning, at the crack of dawn, a few bleary-eyed Australian fans and hundreds of thousands Americans will be wondering if this is the end of an era.
Sam Kerr is almost undoubtedly the greatest NWSL player of all time. She's a league MVP, record-holder for Player of the Month and this season she's broken her own goalscoring records practically every week.
But at Chicago she reportedly only earns around $46,000 per season. It's considerably less than FFA were planning on paying her to stay in the W-League, for instance, but it's a far sight from what she could potentially earn in Europe.
The largest, richest clubs in the world - most noticably English Women's Super League giants Chelsea - want Kerr on their books. Who wouldn't?
These leagues are still in their relative infancy compared to the NWSL, but the professionalism is growing rapidly, even if the competition between the best and worst teams still has a long way to go.
As standards rise, wages are following suit, and so are the expectations.
We've acknowledged before - and it's a consistent theme as you speak to coaches and others heavily involved in the women's game - that the days of female footballers playing in multiple leagues (and multiple sports) are soon going to be a thing of the past.
It might not happen immediately, but if Chelsea sign Kerr, they're going to want her for the full year, not just a few months.
Pre-seasons, training regimes, coaching demands, sponsorship commitments, continental tournaments, internationals and domestic league campaigns...being one of the world's best female footballers isn't a fly-in, fly-out gig anymore.
Then there's the obvious - why would Kerr want to live across three different countries, constantly out of a suitcase (even if it was a very nice one). She might actually want some time off at some stage.
So ultimately, Chicago fans, nostalgic New Jersey natives, and most of all the small Australian contingent who have loved watching the NWSL and all it's done for women's football, prepare for the fact that this might be the last time you ever watch Kerr grace your fantastic league.
And just wait until the next Aussie striker arrives and dominates you all over again.
PS: Our superstar US correspondent Kristin Shaffer will be live-tweeting all the action from the NWSL semi-final for all of us who can't watch the game! Check us out @TheWomensGame
Chicago Red Stars vs Portland Thorns
Bridgeview Stadium, Chicago
Monday, October 21