It's all change for United on the kit front tonight, who are wearing a colour not seen before this season.
Amorim's men will be in their blue change strip to avoid a clash of colours with the red-and-white stripes of Bilbao.
But the eagle-eyed among you will notice United are wearing shorts that are officially 'clear onyx' in colour, almost white.
You have to go back to 2012 for the last time this pair faced off in Europe.
And the history doesn't make good reading for the Red Devils.
Athletic Club KO'd United out of the Europa League on that occasion, winning a two-legged quarter final 5-3 on aggregate.
Ruben Amorim has been keen to talk down United's chances of winning the Europa League.
The Portuguese has claimed even lifting the trophy would not "save" United's horror season.
He explained: "“Lifting a trophy won’t fix our problems.
"It gets us Champions League cash and games , but we need better decisions, better recruitment and to win the fans back with consistency.
"This is just a shortcut- nothing more."
It's all or nothing for Ruben Amorim and Manchester United.
After one of the most disappointing domestic seasons in living memory, the Red Devils have just the Europa League left to save their season.
United haven't had their hands on European silverware since the 2017 season.
And it seems almost unthinkable that after such a disastrous campaign, they're in with a real shout of lifting the Europa League.
That night against Lyon in the last round will not be forgotten in a hurry - and the stars seem to have aligned for Amorim's men in this competition.
Tonight they face a tough test on the road in Spain, with Athletic Bilbao looking to win their first ever Euro trophy.
The final next month is being held at their stunning Estadio de San Mamés - and United are hoping to spoil the party before it even starts.
Kick-off tonight at 8pm, we've team news imminently.