Tottenham's Europa League hopes hang by a thread after Borussia Dortmund eased to a 3-0 win at the Westfalenstadion.
An understrength Spurs side fell behind to Pierre-Emerick Aubameyang's first-half strike on Thursday night, before Marco Reus scored twice to put the German side in full control of the last-16 tie ahead of next week's second leg at White Hart Lane.
From Mauricio Pochettino's team selection to Aubameyang's goal record, here are the main talking points from the game...
Pochettino's rotation policy comes unstuck
Much will be made of Pochettino's team selection after their heavy defeat in Germany, but the Spurs boss insisted he has no regrets following the 3-0 loss
"I have no regrets about team selection," Pochettino said in his post-match press conference. "It was a bad day at the office, we are very disappointed. Sometimes this happens in football, they were better."
It was an honest assessment from the Spurs manager, who turns his attentions to his side's Premier League encounter at Aston Villa on Sunday, but did the Argentine boss miss an opportunity to see how his improving young side would fare against a proven European powerhouse?
With Harry Kane, Erik Lamela and co sitting on the bench, Pochettino may look back at this tie in the coming weeks and wonder 'what if?'
Spurs' mean defence undone
A key component of Tottenham's success this season has been their defence. Whatever the make-up of Pochettino's back four, he has them well drilled which has led to the best defensive record in the Premier League so far this season.
However, Dortmund cut through the Spurs backline with ease, showing their attacking prowess to put three past Tottenham - the first time they have conceded three goals in a game since May 2015 in a 3-0 defeat to Stoke.
It is also the first time Spurs have lost by more than one goal this season as they had no answer to the attacking talents of Reus, Aubameyang and Henrikh Mkhitaryan.
Aubameyang's stock rises
The goals keep coming for Aubameyang. The Dortmund striker has now netted 33 goals in 38 appearances in all competitions this season.
It's that form which has seen him linked with moves to Manchester United, Arsenal, Liverpool and Real Madrid no less.
And if the goals keep coming, then Dortmund may struggle to keep him out of the clutches of Europe's top clubs.
Premier League Spurs' priority
Pochettino has repeatedly shuffled his pack when it has come to the Europa League this season and who could argue with the policy when Spurs, who sit five points adrift of Leicester at the top of the Premier League, are enjoying their best season in years.
Now, with Tottenham's Europa League hopes hanging by a thread after their dismantling in Dortmund and winnable games against Aston Villa and Bournemouth coming up in the league, it would be no surprise to see a similar line-up for the second leg next week.
There is also a trip to Anfield and the visit of Manchester United on the horizon, but should their league campaign start to falter, then the team selection in Dortmund could come back to haunt Pochettino.
Dortmund rightly favourites
It was billed as second in the Bundesliga against second in the Premier League. Dortmund sit five points adrift of Bayern Munich at the top of the Germany top-flight, exactly the same gap from Spurs to Leicester in the Premier League.
But Thomas Tuchel's team looked a class apart and they proved their credentials as Europa League favourites by dismantling arguably England's best option for glory in this competition. The Bundesliga side are now 15/8 favourites with Sky Bet to win the Europa League and they will take some stopping as they look to lift the trophy at Basel's St. Jakob Park in May.
For English sides, the result shows the gap that needs to be closed if an English side is to reach the final of a European competition for the first time in four years.