So, How Did The World's Best Soccer Team Manage Without The World's Best Player?

Barcelona traveled to Paris yesterday to take on Paris Saint-Germain in the first leg of what might be the most intriguing matchup of the Champions League quarterfinals round. PSG, bought by a group of Qatari investors last year, has quickly become one of the richest clubs in the world. This season, they bought forward Zlatan Ibrahimovic and centerback Thiago Silva—arguably the world's best players at their respective positions—from Italian outfit AC Milan. PSG are seven points clear in France's relatively weak Ligue 1, but their goal is to win the Champions League and be crowned world's best club.

Barcelona, the world's best club over the last five years, is the first real test of PSG's ambition. Though they've faded a bit since their height of dominance a couple of seasons ago, they compete in a better league, have better players, and showed in one 4-0 win against AC Milan in the Champions League Round of 16 that they might still be the best European side. And, of course, they have Lionel Messi, who at 25 may already be the single greatest player ever.

A win–or even a tie, really–would do wonders for PSG's chances. But it would be a tall order. Barcelona dominated possession in the first half, largely thanks to their near-perfect passing game, which serves two purposes: the first, obviously, is to keep possession, control the pace of the game, and seek opportunities on goal. But the second is defensive: Barça isn't built to defend. They're tiny. Their outside backs, Daniel Alves and Jordi Alba, are much better coming forward than pedaling backward or tracking players. Carles Puyol is the second-best centerback after Gerard Pique, but Puyol is out with injury. Barcelona don't have another true central defender on their roster. So they turned to the likes of Argentine Javier Mascherano, a 5-foot-9 defensive midfielder who's tenacious, but can't defend aerial play, and dives in on tackles unnecessarily. Barcelona counter the weakness by passing the ball slowly and deliberately, systematically forcing the opposing defense back into their own box, like a vice.

If Barcelona lose possession, they'll pressure the ball intensely with their front three and midfielders until they get it back, and then again squeeze the ball up the field, prodding for holes in the defense. What makes Barcelona special is that most teams in the world can't really score on teams that place almost all their men behind the ball, as PSG did. There's just not enough space. But Barcelona has Messi, and some of the greatest passers in the world. They have the ability to find lanes where other players would only find a wall of bodies. And so they score:

With one pass, Alves beat eight PSG defenders and played the ball directly into Messi's path. There are only a handful of players, let alone defenders, who have the vision and ability to even attempt that pass. Alves is one of them. At half, it was 1-0 Barcelona.

The second half, though, brought surprise and possibly disaster for the Spanish side. Messi tweaked his hamstring just before the break, and was subbed out for Cesc Fabregas. It was a shock for Barcelona and their fans: Messi is their talisman, and even though he's just 5-foot-7 and gets kicked and hacked every game, he hasn't had a significant injury since September 2010, when a sprained ankle held him out for two weeks.

Some soccer pundits and fans think that this Barcelona side without Messi are a shadow of themselves. It'd always been a hypothetical, because Messi barely tires and rarely gets injured, and Barcelona doesn't have many options to lead their attack, so he never gets subbed. But barring a catastrophe or miracle, it's unlikely that we'll see Messi in anything but a Barcelona jersey for another decade.

Messi is in the midst of maybe the most prolific, dominant spell we've ever seen in this sport or any other. In 2012, he broke the all-time record for goals scored in a calendar year, and then kept scoring. He scored in 19 straight La Liga matches and became the first player to score on every opposing La Liga team in succession. He scores about every 60 minutes in a 90-minute game. For context, Ibrahimovic–arguably the top pure forward in the world right now and the most expensive player ever–scores about once every other match.

In a low-scoring game like soccer, having such a guaranteed scorer can cover up a lot of flaws, like lack of size, defensive positioning, and the lack of a second real scoring threat. Messi also pressures the ball on defense with tenacity and athleticism that just isn't sustainable for most players. There are teams in the world—Real Madrid, Bayern Munich, and even PSG—that tend to overpower teams with their attacking play and athleticism, and look well-equipped to beat Barcelona (on paper, at least). Other teams, like Manchester United, likely have the defensive wherewithal and enough match winners to best the Spanish kings. But these teams don't have Messi. To beat Barcelona with Messi, you have to be perfect. To beat Barcelona without him, you just have to be better. Or so the theory goes.

So PSG entered the second half with an opportunity to beat a Messi-less Barcelona. If they lost their home leg, their Champions League hopes would be all but over.

Barcelona still dominated possession, but the side looked a bit toothless. Wingers David Villa and Alexis Sánchez were quiet, and Fabregas often dropped deep into the midfield to collect the ball. There was no depth, and no focus of attack. Villa, still struggling for form after breaking his leg two years ago, was the only other true goalscorer in the side, and Barcelona's best passers had no one to single out. They outnumbered PSG in the midfield, but PSG nullified that by skipping the midfield altogether, electing to play direct balls to Ibrahimovic.

In the second half, PSG manager Carlo Ancelotti brought on three fresh bodies, and slowly, the balance of power began to shift. PSG played long balls, challenging the outmatched Mascherano and Pique, which Ibrahimovic then directed to his second striker and wingers. PSG advanced further up the field and forced Barcelona to defend. When Barcelona got the ball, they didn't have the option of outletting the ball to Messi to work his magic.

And without Messi harassing the ball, centerback Silva often carried the ball himself into the midfield, adding an extra man into the attack. As the game waned on, PSG won dead ball after dead ball. Eleven minutes before full time, they finally finished a free kick. Silva pinged a free header off the post, which Ibrahimovic finished.

Yes, Ibrahimovic was laughably offside, and the goal shouldn't have counted, but PSG deserved a draw. And it looked like they'd get one, too–or even a win!–when Mascherano injured his knee five minutes after the goal.

But Barça reminded everyone of how dangerous a passing side they could still be when a Fabregas no-look, backwards flick found Alexis Sánchez in the box on goal. Sánchez was taken down by the PSG keeper, and Xavi scored the ensuing penalty kick. The away side went up 2-1 in the 89th minute, and the match, along with PSG's hopes at a tie, both seemed to be over.

But Ibrahimovic had terrorized the Barcelona's defense as the target man all day, and finally some good came out of his headers in the waning seconds. PSG right back Christophe Jallet played a looping cross to the far side of the box. Ibrahimovic, marked by a 5-foot-7 Alves, headed the ball down to Matuidi, who was free at the top of the box awaiting the pass. Matuidi struck the ball with his first touch, and the ball deflected and bounced and squeezed under Victor Valdés's arm for the tying goal just before the final whistle.

It felt like a win for PSG at the time, but Barça fans can relax. After conceding two goals at home, PSG has to go to Spain needing a win or high-scoring draw to advance.

The immediate question, of course, is how bad the Messi injury is. Today's reports say the tweak was "not serious," and he will miss a week. This puts him right on schedule to play against PSG again next Tuesday, and we can assume, with Barcelona all but crowned as La Liga champions, that Messi will at least suit up in an effort to lead his side to the next round.

Macherano, however, will miss at least a month. As it is, he was backing up Puyol, who also will be unavailable for the return leg. With few options, Barcelona will likely have to slide defensive midfielder Sergio Busquets into the back line, or insert reserve midfielder Alex Song.

Barça don't need to score to advance, as long as they don't concede. That task becomes that much harder, though, without a suitable centerback to line up next to Pique and battle Ibrahimovic for 90 minutes. As great as Barcelona are, injuries to Messi and Mascherano may expedite a passing of the torch to upstart PSG.