At the same time as Real Madrid faced APOEL at the Bernabéu Stadium, Barcelona traveled to Milan, Italy, to challenge AC Milan away from home. This was the two teams' third encounter of the season.
Barcelona had met AC Milan in the group stage. The two legs had ended 2–2 at home and 2–3 away, and both matches had been extremely dangerous.
Allegri had fielded a depleted lineup for this match. Van Bommel and Tiago Silva were unavailable, while veteran Nesta partnered Mexès in central defense. The inconsistent Bonera also earned a starting spot. All of this was excellent news for Barcelona.
Guardiola had started the match with his strongest lineup. Valdes was in goal, with Abidal, Puyol, Pique, and Alves across the back. Busquets sat deepest in midfield, with Seydou Keita and Xavi in the middle. Iniesta started on the left up front, Messi through the center, and Sánchez on the right wing.
It was easy to tell from the starting lineup just how seriously Barcelona took this match. Guardiola clearly hoped to defeat AC Milan away from home and advance smoothly to the semifinals. Recently, he had also found a tactical system that allowed him to switch repeatedly between three and four defenders.
That was Alves.
When Alves appeared farther forward, Barcelona automatically shifted to three at the back. If the Brazilian right-back dropped back, Barcelona returned to a four-man defense. Guardiola was constantly exploring new ideas through this approach.
But this time, they were facing Italian-style reinforced concrete.
For the first ten minutes, Barcelona, as usual, failed to find its rhythm and form. This had been a common problem for Guardiola's team throughout the past year or two. After ten minutes, Barcelona found its footing, but AC Milan also settled into the match.
The result that followed