A Real Madrid vs. Barcelona Champions League final would be a fitting way to end a season. With the clubs sharing the world’s most publicized rivalry, an unprecedented encounter at the highest level could mark the most memorable game for many years to come.

Both teams are struggling against history. Real Madrid has waited 10 years for a record 10th European title, while Barcelona aims to be the first team to successfully defend a Champions League title since the current format is adopted in 1992.

But like all fantasies, this one may not come true. Both teams suffered defeats on the road this week, with Real Madrid losing 2-1 to Bayern Munich and Barcelona losing 1-0 to Chelsea. Yet, both sides have a reason to be optimistic for next week’s return legs.

Expect a much stronger Real Madrid side. Not only is playing at home a distinct advantage, but several factors in Real Madrid’s defeat may flip.

Cristiano Ronaldo had a difficult game in Germany. A satisfactory performance from Ronaldo on Tuesday could be the difference a Real Madrid victory and a goalless draw.

Bayern Munich coach Jupp Heynckes will most likely opt to settle for a draw in Madrid. The German side will likely play with a deeper defensive line, and allow Real Madrid more time on the ball. With less pressure in midfield, Real Madrid will be all the more dangerous, as Bayern Munich would be exposing its weak defense.

Left-back Philip Lahm may be caught out of position during one of his frequent attacking forays by Angel Di Maria or Kaka. Central defender Jerome Boateng is often considered Bayern Munich’s weak link and could struggle against Cristiano Ronaldo and Karim Benzema.

Real Madrid coach Jose Mourinho is a shrewd tactician, and he will be faced with a challenge at which he usually excels. His teams are built to win 1-0 against top-tier sides.

Mourinho’s former team, Chelsea, has taken a page out of its former manager’s book with an exceedingly negative performance against Barcelona. Content with 38 percent of the possession, the Blues scored on a counter-attack. To be fair, it’s hard to remember the last time in the past four years that Barcelona got out-played.

But Barcelona looked less sharp than usual in its customary dominance. The attack lacked penetration and the midfield lacked inspiration.

Chelsea’s defense, shaped by the Mourinho years, kept Barcelona’s attack at bay. The Catalan midfield is guilty of not providing sufficient opportunities for the forwards. Barcelona star Lionel Messi was lagging safely out of range, searching for the ball.

Barcelona will rely on its near-impeccable home record. Chelsea will count on its status as the one team Barcelona coach Pep Guardiola hasn’t been able to beat.

The one unknowable factor is how much this weekend’s action will weaken the teams. Often, teams participating in high-level European competition rest key players on the weekends.

Today, no side can afford to do so. Barcelona will be playing against Real Madrid in a tightening domestic competition. Both sides will field their best squads in the match that could decide the La Liga season.

Bayern Munich is playing away against Werder Bremen. Though this is a winnable game, the Bavarians are chasing an ever-distant Borrussia Dortmund in the Bundesliga. Don’t expect them to take any chances.

Chelsea has a more difficult fixture, facing Arsenal away. Again, victory will be critical for a team that may not qualify for next year’s Champions League.

This week’s results will hinge on subtle variables. A Real Madrid-Barcelona final looks less likely to happen that it did a week ago, but it is still probable. In a two-leg setting, a setback is not a defeat. All teams should remember that.