Real Madrid may have won the Champions League for the last three years but it seems they’ve found their kryptonite in CSKA Moscow.
The Russian side completed a miraculous double over them in Group G, beating them 1-0 at home and then, in the final group game, thrashing them 3-0 at the Bernabeu.
Despite those two results, it was Real who topped the group, while CSKA finished rock-bottom.
But CSKA will remember their famous night in Madrid for many years to come, despite Santiago Solari fielding a weakened side for the European champions.
However, it was still a starting XI that included Thibaut Courtois, Marcelo, Isco and Karim Benzema.
Gareth Bale, Dani Carvajal and Toni Kroos were also introduced in the second-half.
But there was one player getting more grief from the home fans than the rest - Isco.
The midfielder has struggled for regular first-team football this season with his attitude often being brought into question.
And his actions during the 3-0 loss to CSKA did nothing to endear himself to his fans.
In the 55th-minute, Isco missed an opportunity which resulted in whistles from the home fans.
Spanish outlet Sport are reporting that Isco then turned to the crowd and shouted: “What do you want?”
But, according to Marca, it backfired.
They report that Isco was then booed every time he touched the ball for the next 10 minutes.
After 10 minutes, a section of the stadium then interrupted Isco’s boos by applauding every time he touched it causing the whistling to soon stop.
While it wasn't a particularly damaging result for Real in the grand scheme of things, it may have been a damaging night for the relationship between Isco and the home fans.