Spain has provided the winner of the Champions League each year since 2014 and six of the eight finalists in that time, while four of the last five winners of the Europa League have also been from La Liga.
Of the four Spanish sides competing in Europe's elite competition, only Sevilla managed to pick up a win this week.
Atletico Madrid's draw with Azeri minnows Qarabag has left them facing an almost certain exit from the tournament, which they came so close to winning in 2014 and 2016.
Champions League holders Real Madrid suffered their first group stage defeat in five years after being humbled 3-1 by Tottenham Hotspur on Thursday (AEDT), while league leaders Barcelona were unable to beat an Olympiacos side that are floundering domestically.
Barcelona are still unbeaten and are on track to win their Champions League group while Madrid only need a point to qualify for the last-16, albeit in second place behind Tottenham.
Sevilla's fate is in their own hands after a vital victory over Spartak Moscow, which came two weeks after a shock 5-1 thrashing in the Russian capital.
"It's not got serious yet, but all of a sudden Spanish teams no longer rule in Europe", an AS newspaper editorial said.
"The situation is not a cause for concern at the moment but it is strange to see Spanish teams having this blip after dominating so much in Europe," Miguel Angel Roman, a commentator for broadcaster beIN Sports, said
"I think this is a one-off and we don't yet have the symptoms to declare this a general problem with Spanish football."
Last season Real Madrid became the first team to successfully defend their title since the competition was rebranded in 1992, swatting Juventus aside to win the final 4-1.
They are yet to find that form this season, with their defeat to Tottenham coming just days after their 2-1 shock loss to La Liga debutants Girona.
"Real Madrid are paying for their preparations at the start of the season," Roman said.
"They focused on the Super Cup games against Barcelona and Manchester United which they won very convincingly but that has caught up with them.
"With Atletico we are seeing symptoms of burnout after years under Diego Simeone. They also have a fundamental problem as they couldn't strengthen their squad due to their transfer ban."
While Spanish sides might be underperforming in the Champions League, English sides are experiencing a renaissance after years of underwhelming displays.
Manchester United, Liverpool, Manchester City and Tottenham all top their respective groups after earning wins this week, with the latter two sealing their spot in the last-16, while Chelsea are also in a strong position to qualify despite losing 3-0 to AS Roma on Wednesday (AEDT).
"Several factors have all combined to put English teams at the level they should have been years ago," Roman added.
"We are talking about five teams with extraordinary finiancial potential and an ability to sign the best players around and these teams all have great, innovative coaches.
"But in spite of the delicate situation this week for Spanish sides, I would still count Barca and Madrid as favourites to win the tournament come the end of the season."