They say that soccer games last 90 minutes and, to win, you have to play for the full duration.

But if the Champions League has taught us anything on Tuesday, it is that all you need is one half to close out a two-legged series. In both games of the day, the winning squad killed off any hopes of its opponent of advancing.

Barcelona entered its game with a 3-1 advantage that many felt was sufficient to qualify it for the semifinals. After all, Paris Saint-Germain, Barcelona's opponent, needed a 3-0 or 4-1 goal at the very minimum to advance. But there were already a number of factors against the high-powered offensive French side. First of all, Barcelona had not conceded three goals at home all season. And moreover, the Catalan club coached by Luis Enrique had not lost by a three-goal margin throughout 2014-15. Of course, records are meant to be broken, but any hopes of shocking the world ended effectively for Laurent Blanc's side in the 14th minute when Andres Iniesta dribbled through the entire PSG defense before dishing a tremendous pass to Neymar, who deposited the first of two goals in the opening 45 minutes.

Now PSG needed three goals to push the game to extra time and hopefully penalties, where anything is possible.

But that hope of being the first team to score three goals at the Camp Nou ended 20 minutes later when Dani Alves outwaited Maxwell and flung in a cross that was met by a wide open Neymar for a header tally. It was not 2-0 and PSG needed a 4-2 win to push the game to extra time. But, what made this a tall order was the fact that through the opening half, Barcelona was undoubtedly the better team that dominated possession and created chances. PSG had a grand total of two shots in the first half; none of the shots were on target. In other words -- Mission: Impossible.

Meanwhile in Bavaria, Bayern Munich had a taller task to accommodate than coach Pep Guardiola's former club. Down 3-1 heading into the crucial tie, many thought that the German giants would implode once more in the tournament (last year the side lost 5-0 in the semifinal against Real Madrid). But the defending German champs had other plans, even with the mounting injuries.

And their statement was made to the tune of a 5-0 lead after 45 minutes. Remember how Germany destroyed Brazil 7-1 in the World Cup last summer by conceding five goals in the opening half hour?

Munich did the same thing, but it took 10 minutes longer to get the result. In any case, Bayern needed a quick goal to allay any fears from fans of an implosion, and Thiago Alcantara, who crucially scored the important away goal in the first leg, led the way with an aerial header before the 15 minute mark.

And then the flood gates opened with one mistake after another from Porto. First, goalie Fabiano mistimed a header from Jerome Boateng for the second tally. Then, two brilliant crosses from Phillipp Lahm and Thomas Mueller put Robert Lewandowski in a position to head in the team's third goal. And then a Mueller shot deflected off a defender in before Lewandowski created more magic with a patient snipe inside the box between a defenders' legs. Just like that, it was game over.

Porto never recovered from the first goal and simply made one poor mistake after another. Missed passes. Bayern players finding space to run by defenders. Horrid fouls. It was a mess from start to finish and the team, which needed just one goal to essentially kill the tie early, was kicked out of the building before the halftime whistle had blown; the goal did come but it was the classic tale of "too little, too late." 

The most important outcomes from these games? No one is going to question whether Bayern or Barcelona are contenders. One team manhandled a top club while the other decimated a group of promising up-and-comers with a rout in the opening half of the game.