Villarreal's fairytale Champions League run has caught the imagination of European football - but could quickly turn into a nightmare for Celtic or Rangers.
UEFA rules mean the La Liga underdogs going all the way could potentially stop the Scottish champions landing directly into next season's group stage.
Villarreal shocked Bayern Munich to reach the semi-finals in the under cup knockout specialist Unai Emery, who has already won the Europa League four times.
Next up it's Liverpool as Jurgen Klopp eyes a second Champions League trophy during his time time at Anfield.
If Villarreal do see off the English Premier League title hopefuls they would be just one game away from securing Champions League football.
The Spanish outfit are unlikely to earn a spot through their domestic performance but lifting the trophy would require UEFA to find a place for them in the 2022/23 group stage.
Due to Scotland's coefficient ranking, that could come at the expense of whoever wins the Premiership with Celtic currently leading their rivals by six points.
But how likely is it that this situation will occur?
Liverpool are certainly clear favourites with the bookies to reach the Paris showpiece.
They are heavy favourites to win the first leg at Anfield at 2/7 while the visitors are 11/1 to win and 29/10 to avoid defeat.
In both Champions League knockout games so far this term a first leg advantage has carried Liverpool through, winning 2-0 at Inter Milan and 3-1 at Benfica before failing to win the second leg.
The oddmakers give Villarreal little chance of making the final at a 23/2 long shot to come out on top after two legs, which will offers some consolation to Premiership fans.
And the Spanish club are the clear outsiders to win the trophy with odds of 20/1.
Liverpool come into the game in relentless form with a real chance of lifting the quadruple this season.
Having already claiming the English League Cup, they are pushing Manchester City all the way in the title race, and reached the FA Cup final on Sunday.
They have lost just once in their last 10 games, and that defeat came in the Champions League to Inter - the first loss suffered by Klopp's men in 2022 before they progressed to the last eight on aggregate.
In contrast, Villarreal have saved their best performances for Europe.
They sit in seventh in La Liga as they look to claw back at Europa Conference League spot from sixth-placed Real Sociedad, but have won just one of their last five.
The Yellow Submarine also have no chance of domestic silverware, having been sent crashing out of the Copa del Rey in the last 32 by Sporting Gijon.
It will be a mammoth task for the Spanish side to turn their form around and reach the final - and Rangers and Celtic fans will be hoping the semi-final proves a step too far.
