Barcelona head into the Champions League round of eight as favorites to win it all for the second time in three years.  But before the final, they've got to get through a group of eight teams that offer some serious competition.

Who do they fear the most?  Ahead of tomorrow's draw, let's put ourselves in Pep Guardiola's shoes, and discuss the seven potential matchups awaiting Barcelona.  Number one is the squad most likely to get rolled over by Barcelona, and number seven is the team Pep really doesn't want to see.

Number One: Shalke 04

One of the surprises in the round of eight is Shalke 04, a team nearly thirty points behind in Germany's Bundesliga, but deserving nonetheless of a fantastic run in Champions League.  They represent the most appealing matchup for Barcelona, mostly because of their poor domestic form, especially considering that coach Felix Magath, who led them this far, was recently sacked.

Most impressive are: striker Jefferson Farfan, who scored twice against Valencia, and outstanding young goalkeeper Neuer.  The rest of the team, however, doesn't present the type of physicality to really challenge for a Champions League title.

Barcelona have the added advantage of having knocked Shalke out of the competition three years ago.  This is the match Guardiola is hoping for.

Number Two: Tottenham Hotspur

What a wonderful story Tottenham is in this year's Champions League.  After years of disappointment, they've broken through to the final eight and, fifth in England, are fighting to come back next year.  Tottenham has dangerous players all over the pitch—speed in Bale and Lennon, class with Modrich and Van der Vaart, plus plenty of height in Peter Crouch.

Despite world-class talent and a strong season, Tottenham are just plus-seven in goal differential in the Premier League.  Compare that to twenty, twenty-seven, thirty, and thirty-three for the clubs ahead of them.

While league play isn't always relevant to cup football, these numbers say Tottenham, if they do manage a win at home, aren't likely to run up the score against Barcelona, and they will probably give the Spanish club plenty of chances.

Number Three: Shaktar Donetsk

Another surprising name in the round of eight is Ukraine's Shakhtar Donetsk.  But looking at their league form, perhaps we shouldn't be so surprised.  Shakhtar have won their league five times in the past 10 years (and have finished second every other year), and are top of the table again this season.  They also won the UEFA Cup in 2009.

I won't say that I know a whole lot about this club, but they made Roma look plain silly, scoring some absolute stunner goals in the process.  From what I can tell, they're young, fast, and supremely confident.  Add to that, an away match in a freezing-cold stadium full of crazed fans, and you've got a matchup that nobody wants.

Number Four: Manchester United

Manchester United cruised past Marseille into the round of eight, and are top of the table in the brutal English Premier league.  They've got battle-tested veterans like Ryan Giggs and Edwin Van der Sar, exciting youngsters like "Chicharito" Hernandez, and a legendary coach in Alex Ferguson.  Oh, and Nani, who sometimes looks like the best player on Earth.  So why so high on this list?

Size, strength, and style: all of these characteristics make for a matchup that suits Barcelona very well.  Manchester is not a very big team, and compared to the likes of the rest of this list, nor are they terribly physical.  They'll be without big-man Rio Ferdinand, and they're not likely to "park the bus."  Fortunately for soccer fans, this could make for a very exciting, free-flowing game against Barcelona.

As they did two years ago, Barcelona can overwhelm Manchester.  They can pressure the defense into mistakes, control the midfield, and muscle out the likes of Berbatov and Chicharito.  This is no small challenge for Guardiola's men, but I fancy their chances of rolling right through Manchester United.

Number Five: Real Madrid

This is a matchup that many are dying to see at some point in Champions League.  Real Madrid, while second to Barcelona in La Liga, are getting better and better as the season progresses, and looked very strong against Olympique de Lyon.

Karim Benzema is seeing the regular playing time he needs to excel, Mesut Ozil is having a brilliant season, and Cristiano Ronaldo is still at the top of his game.

But Barcelona has a psychological edge over this team, having beaten them in every "Clasico" since Guardiola took over.  They've managed to overcome Madrid's physical superiority by controlling possession, capitalizing on mistakes, and playing with confidence.

Madrid's squad of recently arrived "Galacticos" is frightening on paper, but still a ways off from being a cohesive team.  New manager Jose Mourinho is still sorting things out.  For this season, at least, advantage Barcelona.

Number Six: Chelsea

Yes, Chelsea has had some mighty struggles in the Premiership this season, but this is a team that really does scare Barcelona.  Nicolas Anelka, who is playing perhaps the best football of his life, is joined up-top by the always scary Didier Drogba, and behind them is a big, strong, angry team very capable of winning the Champions League title.

Chelsea has already proven they can stymie the "tiki-taka."  Barcelona was very fortunate to have beaten them two years ago, and you can bet men like Frank Lampard are licking their chops thinking of having another crack at the little Catalans.  Chelsea has the type of squad that, in the first half of the first game, could score two goals, injure two Barcelona players, and stamp their ticket to the next round.

Number Seven: Internazionale

"Equipazo:" Great team.  Inter knocked Barcelona out of Europe last year en route to a title, and if Barcelona meets them again in the round of eight, they may just do it again.

The following could describe most of the players on this team: unselfish, physical, and smart.  A sturdy back line, a great keeper, and a striker in Samuel Eto'o who just doesn't stop winning titles and scoring clutch goals.  This is truly a team to be feared.

Last year Inter beat Barcelona in a way that infuriated many soccer fans, myself included.  Having secured an advantage in the first leg, they sat back in Barcelona, put 10 men behind the ball, and cleared off play after play.  Ugly, cowardly, unsportsmanlike?  Effective.

Like it or not, that's how you beat Barcelona:  close down the spaces and wait for your chance on the counter-attack.

Inter had an incredible come-from-behind victory against Bayern Munich in the last round—the type of win to motivate and unite a very dangerous squad.  This is the last team Barcelona wants to see in the next round.