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The shadow of the knockout stages of the most prestigious club competition is looming quite emphatically over the Emirates once again.

But given the fact that Arsenal go into this one 2-1 down, this time it might just be exuding an aura of gloom rather than the adventure and hopeful commotion that the North London club is usually accustomed to at this stage.

In my opinion, the reality is far from that.

As much as the hype that is bound to follow in the next few days, I think Arsenal are clear favourites to go through—not only because they were highly unlucky in the first leg, but because of four significant reasons.

1. There is a clear target and a purpose, so complacency would be zero

On a more usual day at the Emirates, we Gooners would, almost invariably, find our side playing "for the crowd," at least in the opening few minutes.

Not in this game.

It's almost certain there will be a no-nonsense approach to this one right from the word go.

The advantage of playing the second leg at home lies not just in familiarity with the ground and the support of the crowd, but also in having a clear idea of what is required.

I've always maintained that when this Arsenal team plays with a purpose, they are good enough not just to beat, but thrash any team...ANY team.

The second half displays in games like Liverpool away, Liverpool home, Bolton home, West Ham away in the FA Cup, and Stoke away are some instances where the performances in either halves have been different as chalk and cheese.

The first 20 to 25 minutes of the second half in the game against Liverpool at the Emirates is still fresh in my mind.

It can almost be described as a blitzkrieg.

I have a feeling this Tuesday night is going to be just that.

2. Porto never scored

There were three goals in that match. Two were scored by Arsenal, and one by the referee.

The scoreline at the "Stadium of the Dragon" did not do justice to the game.

While it is true that they did create other chances, it also won't be going overboard to say that Arsenal did too.

They could not score a proper goal against Arsenal in their own backyard, and Arsene Wenger's men definitely won't make the same mistakes twice in their own.

So advantage Arsenal again.

3. Key players finding their form at the right moment

In a period that, needless to say, is the most crucial in context of both the league and the Champions League, key Arsenal players are finding form.

Emmanuel Eboue, Samir Nasri, Tomas Rosicky, Theo Walcott, and Nicklas Bendtner have tremendously augmented the attacking prowess of the team, and an expected Burnley drubbing on Saturday can further surge the confidence level.

Andrei Arshavin is certain to return too, and given his desire to play in a significant Champions League game for Arsenal, he, without a doubt, would be raring to go and get back into action.

Gael Clichy too would have learnt his lessons about the threat from the right, and given his current form, he should be able to deal with it this time around.

4. The Rambo factor

Get set to witness a different Arsenal side for the rest of the season.

The victory at Stoke has injected a new belief in the team.

The Arsenal that we will soon be seeing in the concluding 10 games of the season and in the Champions League is bound to be highly emotional.

The reaction of the team after the victory was immense.

The huddle reflects the strength of the bond that has now formed and runs through each and every player.

Without a doubt, they would want to do it for Aaron Ramsey, and this would only add to more fuel to their purpose in every game that they will be playing from now on.

Ninety minutes did not prove enough for Arsenal to slay the Portuguese dragon...another 90 should.