Portugal vs. Russia: 5 Key Battles to Watch in World Cup Qualifier

Two sides experiencing vastly contrasting fortunes since the events of Euro 2012 meet in Lisbon on Friday evening, with direct qualification for next summer's World Cup finals in Brazil very much on the line.

While Fabio Capello's Russia have thus far been perfect in their qualifying campaign—four wins from four matches, eight goals scored and none conceded—Paulo Bento's Portugal, favourites to win Group F, have struggled.

Far from convincing, the Portuguese lie third on goal difference and having played two games more than their opponents on Friday evening. Had it not been for a 93rd-minute equaliser from Fabio Coentrao in Israel, their position would be even more perilous.

Therefore, in front of a vocal home crowd, they must win if they're to stand any realistic chance of avoiding a play-off and qualifying as group winners.

However, Fabio Capello's side will be anything but a pushover. With all that being said, here's a look at five key battles to keep an eye on in Friday's World Cup qualifier:

Fabio Capello vs. Paulo Bento

The experienced Italian tactician got the better of their encounter back in October, matching Bento's 4-3-3 formation and being bold in the early stages.

Alexander Kerzhakov's sixth-minute goal gave them the lead and was just reward for their early impetus. From that point on, Capello was happy for his side to defend deep, denying the likes of Cristiano Ronaldo and Nani space and blocking the flanks, frustrating their opponents into long-range shots.

Similar counter-attacking tactics are to be expected again from the away side, tactics which almost led to victory against Brazil in a recent friendly.

Paulo Bento has come under fire in recent times for his rigidity, not wanting to veer away from the 4-3-3 formation which played a key part in their run to the Euro 2012 semi-final. A 4-2-3-1 experiment against Northern Ireland didn't go as planned and was quickly ditched.

Now the Portuguese coach needs to find a way to get the best from his key players, and in turn get the better of Fabio Capello, to lead Portugal to a much-needed victory. Anything less and they stand very much on the precipice.

Alexander Kerzhakov vs. Bruno Alves

Teammates at Zenit Saint Petersburg—although Alves looks set for a move to Turkish club Fenerbahce, according to TurkishFootball.com—the two are doubtlessly well acquainted with one another's games and theirs could well be a key battle on Friday night.

Powerful and commanding, Alves has all the tools and on his day is one of European football's most dominant defenders. However, this hasn't been his best season and he has endured spells out of Luciano Spalletti's starting XI.

While Kerzhakov isn't the type of striker to stand directly up against Alves and become engaged in a physical battle, he is the type to cause the former Porto stopper problems.

Quick and intelligent with his movement, Kerzhakov is clever at both running the channels and dropping into pockets of space from where he can tee up others.

Kerzhakov is far from prolific with the national side—having scored in just two of his last 10 internationals—but he is more than capable of causing the Portuguese back line, and particularly his club mate, problems on Friday.

Can Russia stop Portugal's left side?

With Real Madrid duo Fabio Coentrao and Cristiano Ronaldo having dominion over A Selecao's left side, Russia's right-back Alexander Anyukov could be in for an uncomfortable evening.

The skills of Ronaldo are often eulogised, but Coentrao is a fine attacking outlet in his own right and a good foil for the Portuguese skipper.

The 25-year-old is intelligent, knowing when to offer Ronaldo an option on the overlap—often without hope of receiving the ball from his teammate who uses his movement to veer inside and fire a shot goalwards—and when to merely hold ground to offer a safe passing option.

As a tandem, there are few better in international football who know the intricacies of one another's games. If they are allowed to find their collective rhythm and are given the freedom of their flank then Anyukov, no slouch himself, may not enjoy his night at the Estadio da Luz.

Can Helder Postiga press Russia's back line?

For quite some time Portugal's lack of a world-class centre-forward has been seen as a vital reason for their failings at international level. And while Helder Postiga is a decent striker, top-drawer he isn't.

Thus far in qualifying Fabio Capello's defence has appeared impenetrable, not conceding a goal in their four matches and in all honesty rarely appearing troubled.

However, as Euro 2012 and a November friendly with the United States showed, they are far from infallible.

The CSKA Moscow partnership of Sergei Ignashevich and Vasili Berezutski may be solid penalty box defenders, but they aren't the most mobile nor the best in possession. Postiga, not the most graceful of forwards but a reliable worker nonetheless, will need to press and make their respective evenings as difficult as possible. Do so and he may create opportunities for himself and others.

Dictating with Joao Moutinho

The 26-year-old has long been held as one of Portuguese football's brightest playmakers and it is now eight years since he made his international debut.

A vital part in Andre Villas-Boas all-conquering Porto team in 2010-11, Moutinho will this summer leave his comfort zone in his home country as he moves to France with newly-promoted Monaco.

On Friday evening, on the ground where he is probably most unloved in his home country—having played for both of Benfica's most bitter rivals, Sporting and Porto—he needs to be at his best and dominate proceedings.

Russia's likely starting midfield will encompass Zenit pair Igor Denisov and Roman Shirokov, both tactically very intelligent footballers. Moutinho will need to use not only his excellent range of passing but also his ability to effectively interpret space to dissect that partnership and thus create chances in the final third for Portugal's more threatening goalscorers to have an impact.

Having cost the big-spending French club €25million ahead of his move later this summer, now would be a good time for Moutinho to prove that he is worth every cent.