European club soccer’s biggest night, the final of the Champions League, is only three weeks away, on May 17 in Paris. By tomorrow evening, the two finalists will be known. Possibly they are already known, maybe the first games of the home-and-home semis have revealed all: Arsenal beat Villarreal 1-0 in London, while Barcelona beat AC Milan 1-0 in Milan.

Clearly Arsenal and, especially, Barcelona – with that precious away goal – are the favorites to reach the final. But because, just as in baseball, it ain’t over till it’s over, there’s a chance that things may not work out that way.

Villarreal, for instance, has been upsetting the probabilities all tournament long. The club bears the name of its small hometown on the Mediterranean. Its pint-sized stadium, El Madrigal, holds only 22,000 fans, which is just about half the population of the town. El Madrigal has staged 18 European games, and Villarreal has lost only one of them. In 14 of those games, the opposition failed to score a goal.

That is where Arsenal plays today, against a team that has already knocked Manchester United, Glasgow Rangers, and Inter-Milan out of the tournament.

Coached by Chilean Manuel Pellegrini, Villarreal features six Latin Americans, foremost among them the Argentine midfielder Roman Riquelme. Riquelme may look slow, almost pensive in his play, an anachronism in the swift modern game, but he is the architect of Villarreal’s patient passing game with his superbly inventive playmaking and his brilliance on free kicks.

Villarreal’s biggest problem is that it is a low-scoring team (12 goals in 13 Champions League games) playing against an Arsenal defense that has conceded only two goals in 11 games. The problem is compounded by injury to both its central defenders: Gonzalo Rodriguez is definitely out and Juan Manuel Pena is doubtful.

Facing Pellegrini’s undermanned defense will be Arsenal’s Thierry Henry, a goal-scorer in brilliant form. Behind Henry, there is the 18-year-old Spaniard Cesc Fabregas, who has emerged in just one season as one of the sport’s major midfield talents. Arsenal has had its defensive problems, too. Injuries have sidelined two starting defenders, the Englishmen Ashley Cole and Sol Campbell. Without them, French coach Arsene Wenger fielded a team made up entirely of non-English players – to the extreme displeasure of many in the English soccer community – in the first game against Villarreal.

In today’s game, “we expect Arsenal to play defensively,” Riquelme said. Certainly Arsenal, with its 1-0 lead on aggregate, can afford to be play cautiously and wait to spring the deadly Henry in swift counterattacks. If Arsenal does get a goal, Villarreal have to score three times – hardly likely for a team averaging less than one goal per Champions League game.

A ray of hope for Villarreal may lie in the fact that Arsenal’s Champions League record in Wenger’s 10 years at the helm has been one of failure. Like Villarreal, it is in the semifinals for the first time.

Tomorrow’s opponents, Barcelona and AC Milan, have far more experience behind them. Barcelona has won the tournament once, Milan no fewer than six times. The advantage in the game at the huge 98,000-seat Camp Nou in Barcelona is clearly with the home team. That 1-0 win in Milan two weeks ago puts Barcelona firmly in the driver’s seat – it needs only to tie this game to reach the final.

“If they can win in Milan, then we can win in Barcelona,” was the defiant position of Milan coach Carlos Ancelotti. His team can certainly score goals; it’s averaging 1.8 per game, and features Ukrainian Andriy Shevchenko, the all-time top scorer in the Champions League. Alongside him is the master goal-poacher Filippo Inzaghi, while the Brazilian Kaka is also a goalscorer from midfield.

Defensively, Milan has plenty of experience, but it comes in aging bodies: Paolo Maldini is 37, Jaap Stam 33, and Cafu 35 (and reserve Billy Costacurta is 40!). The defensive stats are not bad – only 10 goals conceded in 11 games – but the trouble is that Barcelona’s stats during this season’s 11 Champions League games are better: 22 goals scored, only four conceded.

Barcelona is generally considered to be the best team in the world, and it is the sparkling attacking play that has caught the attention. The defense, which does it job solidly and safely, has one highly unusual feature: a Mexican star, in the form of Rafael Marquez. It’s very rare for Mexicans to succeed in Europe; only one, Hugo Sanchez, who starred for Real Madrid between 1985 and 1992,became a major star.

The strength of Barcelona’s defense owes a great deal to the team’s attacking skills, to its ability to maintain possession of the ball, and to keep it away from opponents. The attacking part of Barcelona’s game is where the Brazilian genius Ronaldinho rules. FIFA’s World Player of the Year two years running, Ronaldinho has been the key to Barcelona’s success so far, just as he the main reason why Brazil is favored to win the World Cup this summer.

Even on a quiet day Ronaldinho can be the decisive factor – as in the first game against Milan, when his brilliance suddenly flared in the 57th minute: a ravishing turn to fake out Gennaro Gattuso and almost in the same movement a perfect pass to release Ludovic Giuly to score the winning goal.

For Milan, there is an extra edge to this game. The bitter memory of last year’s final in Istanbul, when it was comfortably leading Liverpool 3-0 and suddenly, inexplicably, caved in to give up three goals in six minutes and eventually lose the game on penalty kicks. Six minutes of madness, said Ancelotti. Six minutes that he and nine of his players who were starters that night are desperately eager to erase with victory in this year’s competition.

Not likely, I think. Nor is it likely that Villarreal can continue its giant-killing activities. The final in Paris looks like it will be an Arsenal vs. Barcelona affair. England vs. Spain, if you like … except that Arsenal may well field an all-foreign team, while Barcelona will probably have no more than three Spaniards in its starting lineup.

pagardner@nysun.com