Two teams on opposite sides of the European spectrum take to the field Tuesday in separate ties as the UEFA Champions League knockout stage kicks off.

On one end, there's defending champion Barcelona, who squares off against Germany's Bayer Leverkusen in the first leg of one of the more anticipated pairings in the Round of 16.

On the other end, there's Cyprus' APOEL Nicosia, who became the country's first representative in the knockout stage and became the shock story of the group stage, emerging out of nowhere to capture its group. They'll face Lyon, who had a miracle of their own to reach the knockout phase. 

Here's a closer look at Tuesday's UCL matchups:

BAYER LEVERKUSEN VS. BARCELONA

TV: Fox Soccer Channel, 2:45 p.m.

GROUP STAGE: Barcelona breezed through the top-heavy Group H, only failing to win one match when it played AC Milan to a draw. Leverkusen finished a point behind Chelsea in the more tightly contested Group E, dropping results to Chelsea and Valencia but managing a 10-point haul. 

THE LOWDOWN: Facing a 10-point deficit to Real Madrid in the league table and seeing its hopes of winning a fourth consecutive Spanish league crown continue to slip away, Barcelona can turn its focus to the Champions league, where it has been dominant with the continent's biggest prize on the line.

Leverkusen will look to use their home surroundings to their advantage, but they'll have to overcome some key injuries to do so. Midfielder and rumored MLS DP target Michael Ballack and striker Eren Derdiyok are both expected to miss the match.

OLYMPIQUE LYON VS. APOEL NICOSIA

TV: Fox Soccer Plus/FoxSoccer.tv, 2:45 p.m.

GROUP STAGE: APOEL Nicosia won Group F by virtue of a head-to-head tiebreaker with Zenit St. Petersburg. The only loss the club suffered was in its group finale to Shakhtar Donetsk. Lyon had the cards fall their way in their group finale, overcoming a three-point deficit and seven-goal differential to Ajax on the final matchday to emerge as the runner up from Group D.

THE LOWDOWN: Lyon would be foolish to take APOEL lightly, especially considering the new life it has in Europe following its 7-1 dismantling of Dinamo Zagreb just to reach this stage and considering that it hasn't won a group stage match in its last five attempts. Even so, the Ligue 1 side that is currently on the outside looking in for next year's Champions League is the favorite to advance to the quarterfinals, and putting the pressure on APOEL with a decisive home result is paramount to the club's hopes.

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Who do you see winning Tuesday's games? Think Leverkusen can hold serve at home? Do you see APOEL moving on to the next round?

Share your thoughts below.