Real Madrid and Cristiano Ronaldo might have an edge when they play at Manchester United. Reuters

As he walked toward the locker room last Wednesday, a wry smile broke across Real Madrid manager Jose Mourinho's face. Real Madrid had just drawn 1-1 at home with Manchester United in the Champions League's Round of 16—and you wondered if Mourinho knew something the rest of us didn't.

Conventional wisdom would suggest that United now has the upper hand. United plays the two-legged affair's next 90 minutes—and possibly 30 minutes of extra time and penalty kicks—in front of its own fans. And in soccer, as in most team sports, playing at home offers a distinct advantage. Across Europe's top five leagues, the home team tends to win between 45% and 50% of its games, while the visitors only leave with a win about 25% of the time.

The notion that playing the return leg of a Champions League matchup at home offers some kind of an edge has been a long-held truism in soccer. That is why UEFA, the governing body that organizes the Champions League, seeds teams that win their group and gives them the gift of hosting the second leg.

So playing at home is meant to be a perk. But is it?

In the past four seasons, the team playing away first in the Champions League's Round of 16 has advanced 62.5% of the time. That would suggest a sizable edge—except that seeded teams play away first and tend to be better teams than unseeded teams.

What happens from the quarterfinals on, when clubs are no longer seeded, is a different story: 46% of the teams that were on the road first ended up advancing.

Want a larger sample? There is always the Champions League's little sister, the Europa League. In the past four seasons, starting with the first of the Europa League's three unseeded rounds, teams playing away first advanced just 37.5% of the time.

You can see the logic that would lead organizers to believe there is an edge—but the facts pretty clearly suggest otherwise.

It probably has more to do with how teams matchup than anything else. Take the clash between Mourinho's Real Madrid and Manchester United. Madrid is a team that can be devastating on the counterattack. It has uncompromising defenders who pass the ball accurately when they win back possession, midfielders who can find streaking forwards with accuracy and fast, deadeye frontmen like Karim Benzema and, of course, Cristiano Ronaldo.

Manchester United isn't the kind of side that is comfortable simply sitting back and protecting its advantage—even though that would be the best approach in theory. That is because a scoreless draw would see United advance in the Champions League because of soccer's "away-goals" rule: Goals on the road count double when the overall score is tied.

Yet it is highly unlikely United will do that, partly because it has an attacking philosophy, partly because teams playing at home have a natural impetus to go forward, partly because counterattacking and then conceding a goal requires a difficult tactical adjustment.

Jose Mourinho looks unconcerned during Wednesday's Champions League game. Reuters

That is why the 1-1 home draw wasn't a bad result for Mourinho and Real Madrid. A win would have been better. But a defeat would have been infinitely worse. Throw in the fact that United has conceded more than a goal a game this season—unusual for a top team, let alone the runaway leader in the Premier League—and Real Madrid has averaged nearly two goals away from home and you can see how Mourinho isn't exactly despairing at how things have unfolded thus far.

Would things be that much different if United had played the first leg at home? We'll never know. But it seems obvious that what UEFA passes off as a reward for winning a group may not be a benefit at all. Perhaps a better way is to let the seeded team decide where it wants to play first. That would require a whole new set of decision-making skills, based on how well teams think they know themselves and their opponents.

Ultimately, of course, every team still needs to go and play the games themselves. But in a sport in which everyone seeks an edge, what doesn't seem fair is being rewarded by the powers-that-be with an edge that might be more of a millstone.
