Barcelona and Chelsea met often and contentiously during the Aughts. The Blues beat Barcelona 5-4 on aggregate in the 2004-05 Round of 16. The Catalans returned the favor at that stage in 2005-06, winning 3-2 en route to lifting the trophy. The teams, perhaps cruelly, were then paired together in a group the very next season, though their seminal meeting came in the 2009 semifinals.

England’s Premier League was early 1800s industrial ascendant. Three English clubs made the 2008 quarterfinals (Arsenal and Liverpool were drawn together in the quarters). Cristiano Ronaldo, then playing for Manchester United, won the Ballon D’Or. Abramovich’s Chelsea was down a Mourinho, but still emphatically “Chelsea.” Barcelona, in the midst of a downspell and Ronaldinho’s demise, failed to win the league in consecutive seasons and had finished third the previous year. Messi being the world’s best player was still a debate.

Chelsea did what they had to do. They held Barcelona scoreless in the Camp Nou. They took a 1-0 lead into stoppage time at home. They were heading to Rome for a rematch with Manchester United. Then, in the third extra minute, Lionel Messi found Andres Iniesta just outside the area. The Spaniard shot a frozen rope into the top corner. Ten-man Barcelona went through 1-1 on away goals.

Some Chelsea fans and players felt the fix was in for Barcelona. Not awarding Michael Ballack’s handball in the box, sending off Eric Abidal for breathing on Nicolas Anelka and leaving it until the 93rd minute were surely just part of UEFA’s master conspiracy to make the result more believable. Barcelona went on to upset Manchester United in the final and win their first of two Champions League titles in three seasons. Chelsea changed managers three times and watched their vaunted core descend into senescence. So it goes.

Barcelona Form: The Blaugrana have a 25-2-6 record in La Liga (a down year by their standards) and with 81 points sit four behind rivals Real Madrid and 29 above third-place Valencia. They have had a storming run the past couple months though, winning 11-straight in the league by a margin of 38. This diligence has kept them within range of a title that once appeared lost.

Chelsea Form: Given their expenditure Chelsea have been terrible. They have a 16-8-9 record in the league and are in 6th place with 59 points. They are two points off the Champions League and 23 points behind leaders Manchester United. Since beating Manchester City 2-1 on Dec. 12, the Blues have won just seven of 18 league matches. Abramovich paid $31 million to fire Villas-Boas just months after paying $21 million to pry him from Porto. They have, however, been more formidable at Stamford Bridge, winning 8/11 this calendar year.

Tactics: Barcelona play the Barcelona way, holding possession and picking teams apart through technically precise passing. One thing to note has been their shifting defensive alignments after losing their only natural left back Eric Abidal. Guardiola has used three centerbacks in a line in a 3-4-3 with Dani Alves in an advanced role or used Carles Puyol at left back in a 4-3-3 depending on the opponent.

For Chelsea, caretaker manager Robert Di Matteo has emphasized defensive stability. He made common sense changes: dropping a second midfielder into a holding role in a 4-2-3-1 rather than a 4-1-2-3, pulling the wingers back behind the ball instead of pressing forward and selecting more disciplined players such as Ramires and Kalou. Success has been mixed. The Blues have looked more solid, but have shown little organized ingenuity going forward.

Domestic Distractions: Both clubs have important league matches sandwiched between the two legs. Chelsea likely need a win against Arsenal at the Emirates to qualify for next year’s Champions League. Barcelona could reduce the gap in La Liga to one-point with a win over Real Madrid.

Odds: Using the Soccer Power Index, ESPN’s stats guys make Barcelona 53.9 percent favorites to win the first leg and 82.5 percent favorites to win on aggregate.

Prediction: Barcelona 4-1 Chelsea agg.

[Photo via Getty]