Portugal vs. Spain: Players to Watch in Semifinals Clash

It may be boring to watch, but Spain will put its defense-first approach to its biggest test yet at the Euro 2012 semifinals versus Portugal on Wednesday.

It's hard to criticize Spain's game plan, which has led the team to a four-game unbeaten streak at Euro. It might be frustrating to watch at times, but it has proven to work. 

Cristiano Ronaldo and Portugal, however, could be one of the most challenging opponents La Roja has faced thus far. But then again, there's no better time to focus on defense than when you're facing one of the best offensive players at Euro.

Here's a look at the stars who will be instrumental in Wednesday's all-important clash. 

Xabi Alonso

Recently named the World Player of the Week by Goal.com, Alonso has been instrumental in Spain's four-game unbeaten streak at Euro, and if his team is going to reach the finals, he'll likely have a big hand in it offensively.

The dominant midfielder tallied both of Spain's goals against France in the quarterfinals. He also had 100 touches in his club's hard-fought 1-0 triumph over Croatia in Spain's final match of the group round while completing 89 percent of his passes, according to Goal.com.

He's also been a steadfast defendant of Spain's "boring" approach, which, as far as he's concerned, is giving Spain's fans exactly what they want. He told SI.com's Grant Wahl:

"

They are watching great football games, great football teams. … Most of the teams, we are trying to keep the ball, to have control of the games, and trying to look for the attacking game. That's the best way to look for victory. As we have seen, the teams that are there are because we deserve it. No one takes anything for granted, and you have to play each game as a final, as we will do on Wednesday.

"

Cristiano Ronaldo

Though Portugal got off to a slow start in the group round, it couldn't really be blamed—it was facing Germany, which has been the only team at Euro to win each of its first four matches.

And ever since that opening 1-0 loss to Germany, Ronaldo has been instrumental to Portugal's three successive wins, tallying three total goals in his club's triumphs over Denmark, Holland and the Czech Republic.

Wahl has already called Ronaldo's performance one of the greatest individual performances at a major tournament since 1986—so just imagine what it will mean if Ronaldo keys Portugal to a win over Spain, which is aiming to win its third consecutive major tournament.

Even Spain goalkeeper Iker Casillas recently told the Daily Mail that Ronaldo has yet to fulfill his potential at Euro, so it will be up to him to use his speedy attack to set the tone against stingy Spain. 

Iker Casillas

Spain's goalkeeper hasn't allowed a goal since an opening-game draw with Italy, and if he continues to hold strong, Portugal has no chance.

Casillas will be making his 136th appearance for Spain on Wednesday, and with a win, he will become the first player to tally 100 victories in international football, according to the Daily Mail. But he believes that the biggest factor standing in his way is his Real Madrid teammate. 

Of Ronaldo, Casillas recently told Spanish newspaper Marco (via the Daily Mail):

"

His season at Madrid was incredible in terms of the way he played, the goals and the records. I don't think that right now he is at his best level. … I'll have to be on my guard.

"

Then again, if anyone is familiar with Ronaldo's game, it's Casillas. At least he's prepared.