Athletic Bilbao vs. Barcelona: Score, Reaction from 2015 Spanish Super Cup Leg 1

Barcelona's defensive frailties were laid bare in a 4-0 defeat to Athletic Bilbao in the first leg of the 2015 Spanish Supercopa on Friday night in the San Mames.

Aritz Aduriz registered a second-half hat-trick in the victory, which is the first against Barcelona in a decade, per Infostrada Sports:

According to ESPN Stats & Info, the four goals eclipse Athletic's combined total in their last three matchups with Barca. The 2015/16 campaign may just be getting underway across Europe, but this will undoubtedly be one of the biggest surprises of the season.

For Barcelona, it's another warning sign their defense could be a major issue. The reigning European champions allowed four goals to Sevilla in the UEFA Super Cup. Opta's David Wall provided the grim statistics:

And to think, the biggest questions surrounding Barcelona heading into the first leg mostly surrounded their attack, namely the potential inclusion of Pedro.

The 28-year-old scored the extra-time winner against Sevilla, but he has also been the subject of constant speculation regarding a transfer away from the Catalan club. Former Manchester United striker Andy Cole is doing his part to lure Pedro to the Red Devils:

Before the match, Barcelona manager Luis Enrique sounds as if he's at his wits' end with the whole thing, per Reuters (via the Guardian):

    "Nobody knows at the moment if he will start. I won’t make my decision based on the market. It is a contradiction. He wants to stay but he also wants to have more minutes. I will continue to play those that I think are best for each match. What I am looking forward to though is the end of the transfer window so that everything will then be clear."

Pedro started but was largely a non-factor in the first half. That label could also extend to Barcelona's two other playmakers, Lionel Messi and Luis Suarez. The Spanish league champions mustered just a single shot on target through the first 45 minutes.

It didn't help Barca were staring at a 1-0 deficit in the 13th minute.

Marc-Andre ter Stegen came roughly 20 yards off his line to make an ill-advised clearance. His header landed near the halfway line in the center of the pitch. Mikel San Jose picked up the ball, took a touch and unleashed a screamer with his right foot.

A helpless Ter Stegen could only watch as the ball sailed over his head and into the Barcelona goal. OptaJose provided a helpful visual representation of the goal:

Goal's Ben Hayward believes Ter Stegen should leave the sweeper keeper duties to his fellow countryman:

The goal was particularly important because it allowed Athletic to settle into a nice groove on the pitch. They could afford to sit back a bit and consolidate defensively in their own half.

But Athletic nearly learned the hard way Barcelona can turn the tiniest window of opportunity into a genuine goal-scoring chance. In the 27th minute, Barca broke on the counter. Luis Suarez received the ball on the left side of the box. His cross looked innocuous at first but began curling toward the Athletic goal.

San Jose eliminated the danger with a header off the line.

It's a testament to Athletic's first-half performance that was the only moment Barcelona threatened with an equalizer. Suarez and Messi were almost completely anonymous, with the exception a late free kick by Messi that forced a save from Gorka Iraizoz.

In the second half, the wheels started slowly falling off for Barcelona after Pedro's shot caromed off the crossbar in the 50th minute. He got in behind the Athletic defense but couldn't the most of the chance.

Just three minutes later, Athletic doubled their lead with a rather straightforward goal. Sabin Merino found Aduriz with a solid cross from the left. Aduriz beat the overmatched Javier Mascherano and headed the ball into the back of the net.

Mascherano is a world-class player, but he has and will always continue to struggle when forced to clear out aerial crosses into the box. The 31-year-old was slow to react, and that allowed Aduriz an easy finish.

The Athletic striker made it 3-0 in the 62nd minute, and it was another example of poor defending from Barcelona. Dani Alves—for reasons only known to himself—opted to clear an Athletic cross back across the middle of the 18-yard box.

A grateful Javier Eraso controlled the clearance and quickly passed across to Aduriz, who chested the ball down and placed his shot perfectly in to the far post.

As Spanish football writer Dermot Corrigan noted, the two Athletic goals in rapid succession completely unraveled Enrique's second-half game plan:

Alves further compounded Barcelona's misery by committing a silly foul on San Jose inside the 18-yard box in the 67th minute. That allowed Aduriz to complete his hat trick from the penalty spot, and he promptly sent Ter Stegen the wrong way into the bottom left corner.

At the other end of the pitch, Athletic continued to beat back each and every attacking move from Barcelona. It was the perfect performance in every sense of the word from the home side.

You hesitate to say the Supercopa is already over, but Barca have it all do to in the second leg at home Monday. Not only must they score four goals against Athletic, but they have to hope their so far suspect defense can keep a clean sheet.

Should Athletic Bilbao prevail, it will be their first Supercopa win since 1984-85, the season after they completed a La Liga/Copa del Rey double.