It was a truly classic Clasico after 45 minutes. With end to end action and tremendous pace, it seemed like one for the ages. But the second half fell way below the expectations set by the first half. The game turned ugly and dull to the point of boredom? Why? Because of one man -- Alberto Undiano.

Real Madrid's top stars were blasting the referee after the match with Cristiano Ronaldo going so far as to say that Undiano wanted Barcelona to win.

"We played against 12. It's always the same. They don't allow us. Maybe they wanted Barca back in the league," Ronaldo said according to Soccerway. "If Barca lost today they would have been out. After five years here (in Spain), I understand how things work."

So how did Undiano ruin the game? To set things straight it is essential to note that the referee has now been the main official of the last three Clasico matches dating back to last season. In the first match between these teams in 2013-14, Undiano missed a blatant penalty against Barcelona defender Javier Mascherano after he took down Ronaldo. He missed a similar incident in the game's opening minutes as Dani Alves seemingly clipped Ronaldo inside the box. Later in the half, he overlooked a blatant handball from a Barcelona player off a Ronaldo free kick; he actually missed several from both sides so his consistency is to be lauded here.

However his calls in the second half were laughable at best. Ronaldo earned a penalty shot early in the second half after being clipped by Alves on his way to the box. The problem is that the foul was committed outside the box as replays showed. It was not in fact a penalty. One might argue that the pace of the game makes it hard to make out, but these are the types of judgment calls he is expected to get right most nights and he faltered.

The second penalty call was more laughable. Neymar was given a pass by Messi that put him clear toward goal. Sergio Ramos went after the ball, bringing Neymar down rather easily. Undiano immediately pulled out the red card and awarded a penalty. Ramos was obviously annoyed by the call after the match.

"It's always the same. I didn't touch Neymar but there's no point talking about it, it changes nothing," he said according to Soccerway. "Everyone can see what happened. We could have got something from the game but got nothing.

"There are some things you can't fight against. This was pre-meditated."

One can certainly understand Ramos' frustration. Neymar is a notorious diver and, while there was contact, it was clear that he fell down rather quickly. Undiano should have taken this into account before he not only awarded the penalty but also took out the red. Ramos was far from vicious on the call and there should have been some reconsideration here.

The sending off essentially killed the game and the last penalty was arguably the least controversial. Iniesta split Xabi Alonso and Dani Carvajal but managed to trip over Alonso's leg; Iniesta's fall was rather quick, but it was less of a controversial call than the other two.

However, considering the importance of the game and the timing, one could question why Undiano did not rethink his decisions before being so quick to award a penalty. He let a lot of things fly in the opening half but seemed to be quick in the second when it came to awarding penalties. A poor showing overall by the referee.