Now that the final eight contenders are in place, it's time to look at who could claim Europe's greatest sporting trophy this year. Below are the candidates:
This is the greatest chance Arsenal have had to win the coveted European crown. Some of the top contenders are out, and given the right draw, Arsenal have a great chance of success.
However, a lot of their hopes could ride on the return to fitness of Cesc Fabregas. Additionally, they could be boosted by Robin van Persie's return from long-term injury as we get closer to the end of the season.
Unfortunately, the Gunners have shown that defensive lapses are not uncommon. The first leg against Porto was a classic example of this.
Luckily, their ability to blow opponents away at the Emirates Stadium make them a candidate to reach their second-ever final...and perhaps win their first-ever European Cup.
The main concern for Arsenal, would be a tough draw when they face one of the "big boys." Barcelona may be too great a hurdle for Arsenal to clear.
Mourinho has shown that if his tactics are spot-on, Inter Milan would be a challenge for anyone.
Finally, Manchester United clinically dispatched Arsenal from the competition last year, and completed wins over Arsenal in the league home and away (the latter very comfortably).
Can Arsenal go all the way? Possibly. Although, should they face one of the aforementioned teams, then it would be an incredible achievement.
The current holders demonstrated last night that they are still the team to beat. When on form, Messi alone is almost impossible to keep out for a full 90 minutes.
Add Ibrahimovic, Henry, Iniesta, and Xavi to the mix, and the Catalans' attacking forces are more than satisfactory.
It is difficult to find any weaknesses in this Barca side. Even the often criticised Victor Valdes has proven he can perform to exceptional levels when he is required to (just watch the Champions League final in 2006).
Therefore, Barcelona must still be favourites to win the trophy. Only a perfectly disciplined performance from one of their big rivals could stop Barca's triumph.
Should a team perform like Man United did against the Catalans in the semi-finals of 2008, then Barcelona may struggle. If a team cannot do this, Barcelona must be heavy favourites to retain their crown.
Bayern have fought to make it this far, and I think they might have an ever bigger fight to make it to the semis.
Having struggled to overcome an efficient, but not spectacular Fiorentina side, the deciding goal turned out to be about five yards offside.
Robben and Ribery offer real endeavour and creativity down the wings, but that aside, Munich look out of ideas.
They will have to rely on flashes of brilliance if they are to have a chance of success this year. I just can't see it happening often enough.
The overall package with Bayern is not strong enough to reach the final, let alone win it. I imagine that there will be real concerns in Munich that whoever they meet in the quarterfinals will be too tough to overcome.
The rank outsiders for this year's trophy have been Bordeaux. They have also overcome the odds on several occasions and proven they can mix it with the "big-boys."
Coming through a group with Bayern Munich and Juventus is no easy feat, but Laurent Blanc has put together a ruthlessly efficient team with a very solid backline.
If Marouane Chamakh continues his impressive performances that have earned him admirers all over Europe, then Bordeaux could prove difficult to keep out, as well as difficult to break down.
The final will most likely be a step too far, but I can see Bordeaux springing a surprise and reaching the semi-finals if they can perform on the night.
The Russians showed in Seville that they should not be taken for granted. I personally wrote them off against a very good Sevilla side, but they came up good and showed why they could be contenders.
Impressive performances against Man United in the Group Stages underlined their credentials, though surely a place in the finals would be too much to ask?
Thomas Necid is dangerous in attack, and the increasingly impressive Milos Krasic has earned the plaudits for some excellent displays throughout the tournament. The keeper, Akinfeev, isn't half bad either. His display at Old Trafford reportedly earned him the interest of Alex Ferguson...
Given the right draw, CSKA could reach the semis, but would be very fortunate to make it to the final. However, they would provide a huge test for whoever they meet in the next round, and cannot be taken lightly.
Jose Mourinho showed why Inter are now real contenders. For the last few years, they have not performed at the level they should be at, and struggled against top opposition.
Now they are a real force. Mourinho displays exceptional tactics over both legs against Chelsea...the least you would expect from the Special One.
Wesley Sneijder controlled the game at Stamford Bridge, and with a front line of Eto'o, Milito and Pandev, they could be difficult to keep out.
Should Inter continue this rich vein of form, it would take a brave man to bet against them. However, English opposition have frequently proven the undoing of Italian sides (Chelsea-Inter aside).
The real test of strength would be to see if Inter could beat Arsenal or Manchester United. Then we would know if they are really going to be contenders at the top level.
Lyon are the dark horses for this year's title. Having dispatched the Galacticos of Real Madrid in the last round, they proved they are ready to put their name in the hat of possible champions.
The sale of Benzema has not affected Lyon, and they are very strong at home. Should a team struggle to come away with anything in France, then it could be a real challenge to overturn a deficit against this team.
Lyon cannot be ruled out. The top sides might be too great a challenge for them, but then the majority would have said the same thing about Real Madrid. Just look what happened there.
United are desperate to avenge last year's final defeat to Barcelona, and have another great chance this year.
Wayne Rooney has been exceptional all year round, and his performances will be vital to United if they hope for a repeat of 2008's victory.
On the whole, United are proven contenders. They have a good blend of youth and experience, and the majority of the squad have triumphed in Europe before. With Sir Alex Ferguson at the helm, they can never be ruled out.
United cruised to victories over Arsenal and Inter in last year's Champions League (although this year's Inter are proving to be a different kind of beast), and they demolished Arsenal at the Emirates in the league.
Perhaps their only undoing could be last year's nemesis—Barcelona. However, you would not want to bet against United. They will fight to the last second. 1999 shows that whether they look beaten or not, it's never over for the Red Devils until the final whistle blows.
United will want revenge on Barcelona, and they might be the only team that can get it.